I 



LECTURES 



ITTf >*tl^ 1 



PHYSICAL PHEiNOMENA 



LIVING BEINGS. 

BY CARLO MATTEUCCI, 



PROrESSOR IN THE UNIVERSITV OF PISA. 



WITH NUMEROUS WOODCUTS. 



TRANSLATED UNDER THE SUPERINTENDENCE OF 

JONATHAN PEREIRA, M.D. F.R.S. 

VICE PRESIDENT OF THe' ROYAL MEDICAL AND CHIRURGICAL 
SOCIETV. 



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PHILADELPHIA: 
LEA & BLANCHARD. 

IS-IS, 



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0P33 



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Griggs & Co., Printers. 



To 

MICHAEL FARADAY, D.C.L., F.R.S. 

fullerian professor of chemistry in the royal 
institution. 

Dear Dr. Faraday : 

Professor Matteucci has requested me to dedicate to 
you, in his name, this English edition of his Lectures on 
the Physical Phenomena of Living Beings. With that 
request I most cordially comply. To no one could the 
following pages be more appropriately inscribed than to 
yourself, to whom the physical sciences are indebted for 
some of the most brilliant and splendid discoveries of* 
this prolific age. To no one could I with more pleasure 
address this Avork than to you, for whom I have ever 
entertained the warmest feelings of admiration, respect, 
and esteem. 

Believe me, my dear Dr. Faraday, 
Ever faithfully yours, 

JONATHAN PEREIRA. 

Finsbury Square, Sept. 1847. 



0P33 

•Mi-Si 
4-8 



S 




Griggs & Co., Printers. 



TO 

MICHAEL FAEADAY, D. C.L., F. R.S. 

fullerian professor of chemistry in the royal 
institution. 

Dear Dr. Faraday : 

Professor Matteucci has requested me to dedicate to 
you, in his name, this English edition of his Lectures on 
the Physical Phenomena of Living Beings. With that 
request I most cordially comply. To no one could the 
following pages be more appropriately inscribed than to 
yourself, to whom the physical sciences are indebted for 
some of the most brilliant and splendid discoveries of* 
this prolific age. To no one could I with more pleasure 
address this work than to you, for whom I have ever 
entertained the warmest feelings of admiration, respect, 
and esteem. 

Believe me, my dear Dr. Faraday, 
Ever faithfully yours, 

JONATHAN PEREIRA. 

Finsbur}' Square, Sept. 1S47. 



rREPACE 



TO 



THE ENGLISH EDITION. 



In 1844, Professor Matteucci was appointed by the Go- 
\'ernment of Tuscany to deliver, in the University of Pisa, 
a course of Lectures on the Physical Phenomena of Living 
Beings. These Lectures were subsequently published ; and 
their popularity is attested by the fact, that they have already 
passed through two editions in Italy, and one in France. 

The present translation has been made from a copy fur- 
nished to the Editor by Professor Matteucci, and containing 
a very large number of additions and corrections. Although 
the French edition is, as far as matter is concerned, more 
complete than the Italian ones, it contains, on the other 
hand, numerous errors ascribable to the translator. These 
have been corrected by M. Matteucci, who has also em- 
bodied the results of his most recent investigations in the 
present edition, which must not, therefore, be regarded as a 
mere translation of any of the editions hitherto published. 



VI PREFACE. 

The Editor has introduced some additional woodcuts, and 
has appended a few notes, which it is hoped will increase 
the utility of the work. 

The Editor thinks it right to state that the present trans- 
lation was advertised for publication several months before 
any translation of M. Matteucci's work appeared in the 
medical journfils. 



CONTENTS. 



Dedication ...... 

Preface ...... 

List of Woodcuts ..... 

English Values of French Weights and Measures 



Lect. I. 

II. 

III. 

IV. 

V. 

VI. 

VII. 

VIII. 

IX. 

X. 

XI. 

XII, 

XIV. 

XVI. 

XVII. 

XVIII. 

XIX. 

XX. 



Introduction .... 

Molecular Attraction.— Capillarity. — Imbibition 
Endosmose ..... 
Absorption in Animals and Vegetables 
Dig-estion ..... 
Respiration. — Gaseous Endosmose . 
Haematosis. — Nutrition. — Animal Heat 
Phosphorescence of Organized Beings 
The Muscular Electrical Current . 
Electrical Fishes. — Proper Current of the Frog 
Physiological Action of Gravity, Light and Caloric 
and XIII. Physiological Action of the Electrical Current 
and XV. Nervous Force 



Muscular Contraction. — An: 
Circulation of the Blood 
Vocal Apparatus. — Voice 
Hearing 
Vision. 



mal Mechanics 



iii 

V 

ix 
xi 

17 

29 
44 
80 
98 
117 
134 
154 
176 
190 
212 
224 
254 
296 
309 
332 
345 
360 



LIST OF THE WOODCUTS. 



Figures. Page 

1. Hales's apparatus for ascertaining the force with which powders 

imbibe moisture ..... 39 

2. Hales's apparatus for ascertaining the force with which plants 

imbibe moisture ..... 40 

3. Endosmometer ...... 46 

4. Double.action endosmometer .... 53 

5. Apparatus to illustrate physical absorption . . 86 

6. Hales's experiment to ascertain the force of the sap of the vine 94 

7. Extremity of intestinal villus . . . . Ill 

8. One of the arborescent processes, forming the gills of Doris .Tohn- 

stoni, separated and enlarged .... 118 

9. Phosphorescent organs of glow-worms . . . 171 

10. The galvanoscopic frog ..... 177 

11. The muscular pile ..... 181 

12. Torpedo with one of its electrical organs exposed . 194 

13. Torpedo placed between the sole and cover of an electrophorus 796 

14. Eiectriciil organ of the torpedo .... 198 

15. Brain and cerebral nerves of the torpedo . . . 200 

16. Electrical organs of the torpedo and gymnotus compared 206 

17. Experiment to illustrate the action of a direct and an inverse cur- 

rent on the nerves of a frog .... 231 

18. Three views of Breguel's apparatus for measuring the contrac- 

tions of muscles produced by the electric current . 238 

19. Masson's apparatus ..... 249 

20. Experiment illustrative of induced contraction . . 264 

21. Fragments of Striped Elementary Fibres . . 298 

22. Structure of the ultimate fibrilloe of striated muscular fibre 299 

23. The Anatomy of the Heart .... 313 

24. Red Corpuscles of Human Blood .... 3l6 

25. Poiscuille's ha^mo-dynamometer .... 324 

26. A Front View of Ligaments of Larynx . . . 333 



LIST OF THE WOODCUTS. 



Figures. 

27. A Lateral View of the same .... 

28. A Vertical Section of the Larynx to show its internal Surface 

29. Bird's eye View of the Larynx 

30. A Diagram of the Ear .... 
'M. A Longitudinal Section of the Globe of the Eye 
.32. Diagram explanatory of the Mechani.-m of Vision 
.33. Diagram oxplanat(U'y of Sturm's hypothesis of Vision at differ- 
ent dislanees ..... 

34. Front view of Wheatstone's Stereoscope 

35. Plan of Wheatstone's Stereoscope . 

36. Figures as seen iu the Stereoscope 



Page 
333 
333 
335 
346 
363 
365 

373 
382 

382 
383 



ENGLISH VALUE 



FRENCH WEIGHTS AND MEASURES 



ALLUDED TO IN THIS WORK. 







Troy Gruins. 


Grain (French) 




0-820421 


Once 




472-562500 


Livre 




7561-000000 


Gramme 




15-434023 


Kilogramme 




15434-02344 

Englsh Inches. 


Millimetre . 


. 


0-03937 


Centimetre 


. 


0-39371 


Metre 


• 


39-37100 




Eng. ('ii!>ic Inches. Imp. Pints. 


Litre 


61-028 


= 1-7608 


Hectolitre . 


6102-800 


= 176-08 



PHYSICAL PHENOMENA 



OF 



LIYINa BODIES. 



LECTURE I. 

INTRODUCTION. — GENERALITIES. 

• Argument. — Living beings are endowed with the general properties of 
aU natural bodies. Imbibition. Elasticity. Gravity. Caloric. EleC' 
tricity. Light. Affinity. AH the phenomena of Hving beings are not 
explicable by reference to physical and chemical forces merely. The 
action of physical agents is modified by the organization and molecu- 
lar structure of living bodies. Catalytic actions. The Cell is the ele. 
mentary organ of living bodies; the mechanism of its life explicable by 
the phenomenon of endosmose. Vital phenomena ; a complete explana- 
tion of ihem is, at present, not possible. General conclusions. 
Objects and limits of the study of the physico-chemical phenomena of 
living beings. Precision of language and accuracy of method as 
necessary for physiology and medicine as for the physical sciences. 

Gentlemen, 

I NEVER felt more diffident of my own abilities than now, 
when about to discharge the duty imposed on me, of deliver- 
ing a course of lectures on the Physical Phenomena of Living 
Bodies. But, while I am fully sensible of the difficulties 
of such an undertaking, I am supported by the hope that 
2 



18 INTRODUCTION. LeCT. I. 

my efforts will be rewarded by the great benefitjou will 
derive therefrom. It is perhaps the first time that a course 
of lectures, under this name, has been introduced into 
medico-physical education. We have no work which 
treats exclusively of this subject: the germs, indeed, are 
scattered here and there, but hitherto they have never 
been viewed in the light most favourable for their develop- 
ment. 

If at the commencement of a course of lectures the 
teacher usually finds it requisite to give an exact defini- 
tion of the science he is about to treat of, to show its 
limits and its objects, — in a word, to sketch a plan and 
programme of his course, — assuredly ihe necessity for such 
preliminaries was never more obvious than in the present 
instance. 

General Properties of Living Beings, — Living beings are 
endow^ed with the general properties of all natural bodies. 
The most ultra-vitalist never dreamt of denyingthat living or- 
ganized matter is extended, impenetrable, divisible, and po- 
rous. How can we believe that caloric, electricity, light, and 
chemical affinity, act on these beings in a manner entirely 
different from that which they are known to do on the other 
bodies of nature? 

Yet you will find in some much-esteemed works on 
Physiology, tables of the differences between, and even of 
the presumed opposite characters of, organic and inorganic 
bodies. I should enter into a long and useless discussion, 
were I to attempt to demonstrate to you that many of these 
pretended ditferences have little or no value. Animals 
and vegetables grow by intussusception, minerals bv juxta- 
position ; — in other words, in the former, growth takes 
place by internal juxtaposition, in the latter by external 
juxtaposition ; for organized bodies conceal in their interior 
the dissolved elements of new formations, whilst, on the 



LeCT. I. IMBIBITION — ELASTICITY. 19 

contrary, these elements are situated externally in the case 
of inorganfc bodies. 

During life there is a continual struggle between the 
physical and vital forces ; death is the triumph of the for- 
mer over the latter. But shall this be deemed a sufficient 
proof that vital and physical forces are essentially distinct, 
and opposite in their modes of action ? Would it be cor- 
rect to say, that the different parts which together form an 
arch are endowed with a force opposed to gravity merely 
because they do not fall ? 

Imbibition.— Organized living beings, like all other bodies 
in nature, are extended, impenetrable, divisible, and porous. 
Plunge the n^^nto water, or any other liquid, and you will 
find that, like sand, pounded glass, porous substances, and 
bodies formed of capillary tubes, they imbibe. This pro- 
perty is of the greatest importance to them. In a great 
number of animals, life may be suspended for a considera- 
ble time with impunity ; but, on contact with water, which 
they have the power of imbibing, they return to life, and 
recommence their movements. Who is ignorant of the 
beautiful experiments made by our illustrious countryman, 
Spallanzani, on the rotifera ? Observe this tendon and 
this membrane ; they are hard and shrivelled. One might 
suppose that they never could have formed any part of an 
organized body ; yet, if we plunge them into water, it will 
be seen that, in proportion as they imbibe moisture they be- 
come soft, supple, and elastic, and assume that condition 
which in the living body, fits them for fulfilling those func- 
tions for which they were ordained. 

Elasticity. — Elasticity belongs to living beings as well 
as to other bodies of nature. Here are pieces of intestine 
and of artery ; I can stretch or compress them more or less 
as I please. If I open this stop-cock, which is fixed to 



20 INTRODUCTION. LeCT. I. 

the trachea, you perceive that the lung collapses ; whilst 
it swells up and expands again when I force ^ir into it. 
Do not imagine that these different organs could fulfil 
their respective functions without the elasticity of the pa- 
renchyma of the lung, of the intestine, or of the artery. 
Destroy this, and these functions are stopped, or at the 
least they are altered. 

Gravity. — Gravity acts upon the solid, liquid, and 
gaseous parts of living beings, as on all other natural 
bodies. We could never explain the functions of respira- 
tion and absorption if we did not take into consideration 
the physical properties of the solids, liquids, and gases of 
the economy, and their conditions of equilibrium. 

Caloric. — Apply a sufficient degree of heat to an orga- 
nic body, and you will observe the evolution of gas, the 
disengagement of aqueous vapour, and the combustion of 
carbon and hydrogen in the air, producing carbonic acid 
and water. If at first the heat frequently hardens and 
shrivels organic matters, instead of dilating and liquefy- 
ing them, as it usually does with inorganic substances, you 
cannot surely attribute this difference to vital action, since 
life has long been extinct when these phenomena appear. 

All these effects are owing to a peculiar structure and to 
the physico-chemical properties of the elements of which 
the tissues are composed. In fact, organized beings, when 
subjected to the action of heat, first lose the water with 
which they are impregnated, — an effect which commences 
in the part to which the heat is most directly applied ; the 
substance then curls up like horn, just as a piece of paper 
does which has been moistened more on one side than on 
the other, the largest surface forming the convexity of the 
new shape produced by the contraction. 

These organic bodies often contain albumen, which coa- 



LeCT. I. PHENOMENA OF LIVING BEINGS. 2l 

gulates under the action of a strong heat ; their elements 
separate in the gaseous form, producing more simple and 
consequently more stable combinations. 

Electricity. — The electrical discharge traverses organized 
bodies, and diffuses itself in their interior with more or less 
facility, according to their different degrees of humidity. 
When the spark passes through them, it volatilizes and 
burns them, reducing them to ashes. When the electric 
current traverses the fluids of living beings, it effects the 
decomposition of the salts contained within them ; acids 
being evolved at one pole, bases at the other. Albumen 
coagulates at the positive pole, where oxygen and a frothy 
acid liquid are set free ; hydrogen appears at the negative 
pole along with an alkaline liquid. 

Light. — With regard to the luminous rays, no one can 
be ignorant of the fact, that in traversing the humours of 
the eye they deviate from a right line, sometimes diverging, 
sometimes converging, according to the different density of 
the humours and the conformation of the parts which con- 
tain them, as in a dioptric instrument. 

Jiffinity. — Let me add, that the elements of which human 
beings are composed are always obedient to the general laws 
of affinity; the chemist can recognise and separate them by 
the ordinary process of analysis. Subject them to the in- 
fluence of chlorine, bromine, or iodine, and hydrogen will 
be the first element which will be separated to combine 
with these metalloids and form hydracids. 

All oxidising agencies, when tolerably energetic, convert 
organic matters into acids. 

Phenomena of Living Beings. — From these considerations 
are we to conclude that all the phenomena of living beings 
are expUcable, by the general properties which belong to 
them in common with all the bodies of nature, and by the 
sole action of the great physical forces, caloric, light, elec- 



22 INTRODUCTION. LeCT. I. 

tricity, and attraction ? Such an inference would be as far 
from the truth as the conclusion of those who have denied 
and still deny these general properties to living beings, and 
who regard them as entirely beyond the influence of phy- 
sical agents. 

Examine those phenomena of living bodies, which, if I 
may be permitted so to call them, are the most physical, the 
most chemical, and you will find considerable differences in 
the mode of action of physical and chemical agents in the 
organism, — differences which are inexplicable in the present 
state of our knowledge of the laws governing these forces. 
Does not the phenomenon of vision itself, which may be 
termed a purely physical phenemenon, present peculiarities 
which remain up to the present moment unexplained? If 
the latest discoveries in science enable us to account for 
the distinctness of vision at all distances, and the absence 
of colour on the edges of the image, how, by the aid of phy- 
sical laws, can we explain the perception of a single object 
in its natural position, by a double and inverted image? 
What could we not say of hearing and the voice, which are 
simply effects of some particular vibrations of the air, propa- 
gated by solids, according to the general laws of acoustics? 
To questions such as these science can give no completely 
satisfactory answer. 

Organization. — The chemical action of light, which de- 
composes carbonic acid, carries the carbon under the form 
of new combinations into the interior of vegetables, disen- 
gages the oxygen, and thus produces what the most pow- 
erful chemical affinities cannot accomplish, is certainly dif- 
ferent from that which decomposes some oxides and me- 
tallic chlorides, an effect for the production of which the 
feeblest chemical actions are sufficient. Apply an electric 
current to the nerves of a living animal, and the peculiarity 
of the resulting phenomena will prove to you the immense 



LeCT. I. ORGANIZATION. 23 

difference which exists between the effects of the great 
forces of nature, according as the body in which they oc- 
cur is living and organized, or inorganic and dead. 

What, then, is the cause of these extraordinary differ- 
ences in the modes of action of physical agents on living 
beings and on other bodies of nature ? Here is a primary 
question of the highest importance, and one to which the 
existing state of our knowledge furnishes no satisfactory re- 
ply. But let us not, on that account, abandon the analogies 
which the physical sciences offer us ; a ray of light which 
penetrates a piece of glass or a body of w^ater, in an oblique 
direction, deviates from the straight line, whilst, on the con- 
trary, if it fall on a crystal of carbonate of lime (calcareous 
spar) it is split into two other rays, each of which deviates 
from the direction of the primitive ray, but in unequal de- 
grees. The cause of the difference of these phenomena 
resides in the difference of physical structure existing be- 
tween glass and crystallized calcareous carbonate, and per- 
haps also in the different chemical nature of their molecules. 
These modifications of the luminous ray, however, arise 
more from diversity of structure, or the peculiar arrange- 
ment of the molecules, than from differences of chemical 
composition. Indeed, w'e know that glass acts differently 
upon rays of light, according as it is more or less com- 
pressed in different directions, without its chemical compo- 
sition undergoing any change. 

Who could confound an organized being with an inor- 
ganic body ? In these groups of closed vesicles, of diffe- 
rent dimensions, united and disposed in arTirregular manner, 
there is assuredly something essentially different from a mass 
of polyhedral particles, composing a crystal. To say, with 
some micrographers, that organization is crystallization ef- 
fected in a liquid which the first formed crystals imbibe, is 
equivalent to admitting that the structure of a stalactite is 



24 INTRODUCTION. LeCT. I. 

identical with that of the lungs and the liver. Molecules, 
composed of at least three elements, into each of which a 
great number of elementary atoms enter, must necessarily 
form chemical systems, whose affinities differ from those 
which are possessed by molecules chiefly composed of two 
elements, and in which the number of elementary atoms is 
smaller. And if the general chemical actions, by showing 
us that combinations become weaker in proportion as the 
number of the elementary atoms increases, are sufficient to 
explain the tendency of organic bodies to resolve themselves 
into more simple combinations ; if chemistry furnishes us 
with many instances of this same tendency in some inor- 
ganic compounds whose composition has many analogies 
with that of organic bodies, it is not, therefore, to be. in- 
ferred that the laws of inorganic chemistry are sufficient to 
give us a complete explanation of all the chemical pheno- 
mena of life. We must then conclude that organization 
and the molecular structure of living beings effect impor- 
tant modifications in the action of physical and chemical 
agents. 

Actions of Contact or Catalysis. — We must not, however, 
omit to add that each successive day increases the number 
of a particular class of chemical phenomena whose expla- 
nation is impossible by the ordinary laws of affinity only ; 
I refer now to actions of contact or catalysis. In the greater 
number of these we find that a substance, usually in very 
small quantity, excites in other compounds, without itself 
undergoing any modification, considerable changes either 
of chemical composition or of physical properties. To this 
category of phenomena belong the various kinds of fermen- 
tation. We shall find that the number of catalytic actions 
in living beings is immense. Admitted. We can also 
produce them in our laboratories ; they are of the same 
nature as those which platinum black effects on a mixture 



LeCT. I. VITAL PHENOMENA NOT EXPLICABLE. 25 

of hydrogen and oxygen, and which finely divided silver 
produces on peroxide of hydrogen. 

Cell-life. — I ought here also to mention a fact of importance 
which I shall have occasion hereafter to speak of more fully. 
The cell is certainly the elementary organ, the molecule of 
organic bodies. We can now by the aid of the pheno- 
menon of endosmose alone, effected entirely under the 
dominion of physical forces, explain the mechanism of cell- 
life ; we can tell how the materials necessary for nutrition 
are able to penetrate the cell, whilst others are eliminated. 
We shall go over together an extensive series of physio- 
logical facts, of which endosmose has furnished the expla- 
nation. 

Vital Phenomena not completely explicable. — We may also 
add, and we intend to demonstrate the fact to you, that light, 
heat, and electricity are produced in living beings, by the 
same physico-chemical actions as those which take place in 
inorganic bodies, and that they offer the same results. But, 
with the aid of this knowledge and of these analogies, dare 
we hope to obtain a complete explanation of all the phe- 
nomena of living beings? For the present, at least, this 
would be a vain hope. 

Open an animal, examine its kidneys and its liver, and 
then ask yourselves by what physical force you can explain 
how the blood, which is carried to an organ, forms bile and 
urine. Can we, by having recourse to chemical affinities, 
however modified, and aided by the peculiar structure of 
the organs, and even also by the actions of contact, — can 
we, I will not say comprehend, but even obtain a glimpse of 
the way in which the various organs effect the separation 
and transformation of the constituent parts of the blood, in 
which all the organic elements are mixed, partly suspend- 
ed, partly dissolved, and of which they have need in order 
to repair their continual losses? What can we say of the 
functions of the nerves and generation ? 



26 INTRODUCTION. LeCT. I. 

Conclusions.— We conclude, therefore: — 

1st. That living beings have the general properties of all 
the bodies of nature ; that these properties are influential 
in the production of the phenomena proper to them ; and 
that, consequently, we must not neglect or disregard them 
when we attempt to explain these phenomena. 

2dly. That the great physical agents, caloric, light, elec- 
tricity, and molecular attraction, act on living beings as well 
as on all the bodies of nature, and that their action must 
necessarily be influential in the production of the functions 
peculiar to these beings. 

3dly. That these forces, when acting on organized mat- 
ter, sometimes have their general mode of action modified, 
and that this difference is owing to a diversity in the struc- 
ture and chemical composition of organized bodies. 

4thly. That there are also in living beings phenomena 
which w^e call vital ; that these are numerous and of the 
highest importance, and that, in the present state of science, 
we are unable to explain how their production can be in- 
fluenced by physical agents, though the action of these be 
modified by the organism. This is the reason that we have 
a study, — a science w^hose object is the physico-chemical 
phenomena of living bodies ; as there is one for experimen- 
tal physiology. The intimate and necessary connexion is 
found in the third class of facts which we distinguished. 
Organization modifies the action of physical agents, and 
the study of these modifications requires the co-operation of 
physics and experimental physiology. Do not forget that 
we have formed a fourth class of phenomena of living beings, 
which we have called vital. I term them vital phenomena 
not vital forces, and indeed the diflference is truly vital. 

If Newton had called the force which rules the wondrous 
system of the celestial machine merely attraction, or attrac- 
tive force, his name would long since have fallen into ob- 



LeCT. I. PHYSICO-CHEMICAL PHENOMENA. 27 

livion ; but by demonstrating that attraction is exercised in 
the direct ratio of the masses, and in the inverse ratio of 
the squares of the distance, and by thus unfolding the eter- 
nal laws of this force, Newton has rendered his name ira- 
mortal. 

To speak of the vital forces, to give them a definition, to 
interpret phenomena by their aid, and yet to be ignorant of 
the laws which govern them, is doing nothing, or rather it 
is doing what is worse than nothing. It is to attempt an 
impossibility, it is to content the mind to no purpose, to stop 
the search after truth. To state that the liver separates the 
elements of the bile from the blood by means of the vital 
force, is merely to assert that the bile is formed in the liver. 
By thus varying the expression a dangerous illusion is esta- 
blished. 

Physico-chemical Phenomena. — I believe that I have clear- 
ly shown the object we ought to aim at in studying the phe- 
nomena of living beings, which returns in its ultimate ana- 
lysis to the examination of the physico-chemical phenomena 
of these bodies, of the modifications which organization 
effects in the general action of physical agents, and, lastly, 
to the investigation of the laws, at present empirical, of the 
purely vital phenomena. 

I hope I have succeeded in fully determining what are 
the limits within which we ought to confine ourselves, in 
the vast domain of physiology, and what part of the subject 
we ought to study under the title of the physico-chemical 
phenomena of living beings. The generalities which I have 
now stated must be sufficient to prove the importance of 
understanding the functions of living beings. 

Precision of Language. — In these lectures I propose to 
myself another, and not less important, object; it is to in- 
troduce, in the exposition of physiological facts, and in the 
investigation of their laws, that precision of language, that 



28 INTRODUCTION. LeCT. I. 

exactitude of expression, that rigorous method, which are 
too often discarded in the study of physiology and of medi- 
cine, and which have hitherto been almost exclusively 
characteristic of the physical sciences. 

Every advance in this direction, however slight it may at 
first appear, will in fact be of great importance to physio- 
logy; it will be a certain conquest gained, since it will be 
founded upon knowledge, independent of the science of 
the organism, and of which the bases will be established 
and supported on physical theories, each proposition of 
which has been rigorously demonstrated by experiment. 



LeCT. II. MOLECULAR ATTRACTION. 29 



LECTURE II. 

MOLECULAR ATTRACTION ; CAPILLARY FORCES ; IMBIBITION. 

Argument. — Necessity of food for living beings. Capillary attraction, 
imbibition, and endosmose require to be studied on account of iheir 
agency in the phenomena of absorption and exhalation. Capillary at- 
traction, phenomena of; theory. Imbibition, phenomena of; differs for 
different liquids and at different temperatures. Its agency important 
in animals and plants. Hales's experiments on the imbibition of plants; 
his results due to atmospheric pressure. The effects of chemical affinity 
produced by capillary forces and molecular attraction ; fresh water ob- 

. tained by the filtration of salt water through sand. 

Every one knows that a living body requires, for its con- 
tinued existence, the constant introduction of new sub- 
stances into its system. These substances, the greater 
number of which are solids, are transformed and reduced 
to the liquid state by means of certain functions of the 
organism. In this state they pass into particular cavities, 
from whence, after having undergone other transformations, 
they escape. We saw, in the first lecture, how the porosity 
of the tissues of living beings allowed them to imbibe and 
to become impregnated with those liquids with which they 
came in contact. We cannot, therefore, give you a satis- 
factory account of the phenomena of absorption and exhala- 
tion without considering the part which is played by capil- 
lary attraction, imbibition, and endosmose, — phenomena 
which, as we already know, can be exercised by inorganic 
bodies. The importance of studying these two functions is 
so great, that I purpose devoting the whole of this lecture 



30 CAPILLARITY. LecT II. 

to the examination of the purely physical phenomena of 
capillarity and imbibition; in order that, by means of the 
information thus communicated, you may be enabled to 
judge what part they play in the functions of absorption and 
exhalation. 

Capillarity. — As I purpose to confine myself to a simple 
detail of facts, I shall here state, in the form of propositions, 
the principal results, drawn from observations, of the phe- 
nomena of capillarity. 

1st. When a body is plunged into a liquid, the latter is 
either elevated or depressed around the solid, and presents, 
at its point of contact with it, a concave or a convex surface, 
according as it is either elevated or depressed. In the first 
case, the immersed body is said to be wetted or moistened, 
as when glass is introduced into water ; in the second case, 
of which the immersion of glass in mercury is an example, 
the solid does not become moistened. 

2dly. When we plunge two bodies suflSciently near to 
each other into a liquid, the latter is either elevated or 
depressed between them, according as they are or are not 
moistened by the liquid. It is requisite that the two bodies 
should be so near to each other that the two curved surfaces 
formed by the liquid may touch. The elevation or depres- 
sion of the liquid above or below its level, is in the inverse 
ratio of the distance of the two bodies from each other. 

3dly. If we plunge, into a liquid, a glass tube open at 
both extremities, the liquid rises or falls in the tube, and the 
effect is greater in proportion to the smallness of the bore 
of the tube. If we compare the elevation or depression 
Avhich takes place in a cylindrical tube, with that which is 
observed between two glass plates separated from each 
other by an interval equal to the internal diameter of the 
tube, it will be found that the elevation or depression in the 
tube is twice as great as that between the glass plates. The 



LeCT. II. LAWS OF CAPILLARITY. 31 

liquid rises and adheres to the glass or moistens it ; on the 
contrary, it falls in the tube, if the liquid be not able to 
moisten it. 

In a tube of 1 millimetre [about ij of an English inch] 
in diameter, the water rises 30 millimetres [about \\ English 
inches ;] and mercury falls 13 millimetres [about \ an Eng- 
lish inch.] It will be readily admitted that capillary actions 
must exercise great influence over the functions of the tissues 
of animals and vegetables, when we reflect that the inter- 
stices and the capillary tubes of the tissues have a diameter 
of from y^^ to jI-q of a millimetre [about the ^^l^^ to about 
^-q\-q of an English inch.] 

4thly. The concave surface of the elevated liquid, and 
the convexity of the depressed liquid, belong to a hemis- 
phere whose diameter is equal to that of the tube. 

5thly. If a drop of water be introduced into a conical 
glass tube [held in a horizontal position] it will run to the 
narrower end ; but if a drop of mercury be introduced, it 
will, on the contrary, run to the wider end. 

6thly. The phenomena in question are entirely indepen- 
dent of the volume of the solid body plunged into the liquid, 
and consequently the thickness of the sides of the capillary 
tube, in which they are observed, is without influence on 
them. 

Tthly. These phenomena occur equally in air at the ordi- 
nary pressure, in condensed or rarilied air, in a vacuum, 
and in any gaseous medium. 

Sthly. All bodies, of whatever nature, yield, if susceptible 
of being moistened, the same results, provided that before 
immersing them in the liquid we make a layer of it adhere 
to them. 

9thly. For the same liquid, and with the same tube, the 
elevation or depression of the interior liquid column is in 
proportion to the temperature of the liquid, and in a greater 



32 MOLECULAR ATTRACTION. LeCT. II. 

ratio than that of the diminished density produced by the 
heat. 

lOthly. The elevations and depressions of which we have 
just now spoken, are independent of the density of the 
liquids. Thus, if we represent by 100 the elevation of 
water in a tube, that of alcohol will be 40, that of the vola- 
tile oil of lavender 37, and that of a saturated solution of 
common salt 88. 

llthly. Two bodies within a certain distance of each 
other, and floating upon a liquid, mutually attract each 
other and adhere, provided that both or neither of them be 
susceptible of being moistened. If one only be susceptible 
of being moistened, they repel each other. On this prin- 
ciple we explain the tendency possessed by small light 
bodies floating on water, to approach the sides of the vessels 
containing them. 

12thly. Whatever be the height to which a liquid rises 
it never flows over the upper opening of the capillary tube. 
This indeed is a necessary consequence of the facts already 
stated. For it must be remembered that the surface of the 
column of liquid elevated in the tube is always concave 
outwardly. Hence if we pour water into one leg of a bent 
capillary tube until the column terminates by a surface at 
first horizontal, then convex outwardly, it will be found 
that the other column of liquid remained concave, and is 
constantly more elevated than the other. Thus then, in the 
phenomena of capillarity, a force of depression is developed 
when the surface becomes convex. Do not suppose that 
the water which drips from a wick of cotton moistened 
with this liquid, and of which one end is bent downwards, 
does so by reason of capillarity ; for we have only to hold 
the wick horizontally, and the discharge immediately 
ceases. 

Theory. — I cannot dwell on these phenomena so far as to 



LeCT. II. MOLECULAR ATTRACTION. 33 

give you the theory, which belongs entirely to the domain 
of the highest mathematical analysis. The experimental 
results which I have adduced are sufficient to prove that 
the phenomena depend on that force which we call mole- 
cular attraction — a force which is exerted between the 
molecules of the solid and those of the liquid, and between 
those of the liquid itself, and which ceases to act imme- 
diately the smallest [appreciable] intervals separate the 
molecules. 

To avoid any false application of the phenomena of ca- 
pillary attraction to the animal economy, it must be con- 
stantly borne in mind that a space completely filled with 
liquid is incapable of exercising any capillary influence ; 
that the action of a capillary tube on liquids is due, less to 
the substance of the tube, than to the nature of the liquid 
with which its inner surface is moistened, and, finally, that 
liquids never overflow the upper aperture of the tubes in 
which they are elevated, by the mere agency of capillarity. 

Imbibition. — The phenomena of Imbibition^ of Hygros- 
copicity, &c. are generally of the same nature as the pre- 
ceding, and depend on the same force. A piece of sugar, 
a wick of cotton, and a cylinder of sand, of ashes, or of 
sawdust placed in contact with water, or any other liquid 
which moistens them, immediately draw up the liquid into 
their whole mass ; that is to say, they imbibe it. It is the 
same with certain tissues, as cartilages and tendons, which, 
being dried and then plunged into water, resume in a few 
hours all the properties they possessed during life. This 
effect is the result of the action of the absorbed water. So 
also in the celebrated experiments with the rofiferdy which 
are restored to life and motion when moistened by a drop 
of water. 

The phenomena of imbibition have an influence on the 
filtration of liquids. For when these hold in suspension 
3 



34 MOLECULAR ATTRACTION. LeCT. II. 

solid particles, the latter are separated and left on the filter, 
the substance of which imbibes the liquid. When a drop of 
chocolate or ink falls upon cloth or filtering paper, it pro- 
duces a dark central spot, surrounded by a zone of a paler 
coloured liquid. The same effect takes place when blood 
is extravasated in the sub-cutaneous cellular tissue ; the 
serum extends to the margins, and separates from the co- 
louring matter. 

In the phenomena of imbibition, we have to consider first, 
the force of adhesion between the liquid, and the surfaces 
of particular solids placed in contact with them, and after- 
wards capillary action, properly so called ; for in sugar, in 
a mass of sand or of ashes, and in organized tissues, there 
certainly exist very minute cavities, which ramify internally 
in a more or less tortuous manner. 

Imbibition of different Liquids. — The phenomena of im- 
bibition deserve to be more attentively studied than they 
have yet been. I shall lay before you the results of some 
experiments which, in conjunction with Professor Cima, I 
made on this subject. I wish that it had been in my power 
to have extended them. 

We filled some tubes of glass of two centimetres [about 
f of an English inch] with very white sand, which had 
been sifted through a very fine sieve. The extremity to 
be immersed in water was closed by a piece of cloth. We 
had previously taken the precaution of drying the sand in 
a salt-water bath. It was then introduced by the upper aper- 
ture of the tube, care being taken not to shake it when the 
tube was full, lest the sand within should become unequally 
compressed. Six tubes thus prepared were plunged at the 
same instant into six different liquids, at a temperature of 
-}- 12° centig. [= 53-6° Fahr.]. The action of imbibition, 
by which the liquids were elevated in the tubes, continued 
for ten hours, at first being rapid, but gradually becoming 



LeCT. II. IMBIBITION OF DIFFERENT LIQUIDS. 35 

slower until it ultimately ceased. Each tube was plunged 
into its liquid to a depth of about J centimetre [about I Of 
an English inch ;] and in order that this depth should re- 
main constant, we added, from time to time, more liquid. 

The following are the greatest heights to which the 
different liquids rose. All the saline solutions were of 
the same density, viz. 10° of Baume's areometer [sp. gr. 
1-075.] 

Millim. 

Solution of carbonate of potash - - 85 

Solution of sulphate of copper - - 75 

Serum of blood 70 

Solution of carbonate of ammonia - - 62 

Distilled water 60 

Solution of common salt - - - 58 
White of eggj diluted with its own volume 

of water ----- 35 

Milk 55 

This table shows how much imbibition differs in the case 
of different liquids : in solutions thickened with gum, with 
boiled starch or with oil, scarcely any imbibition takes place; 
and it is also very feeble in concentrated saline solutions 
and in all liquids holding very finely divided particles of 
solid matter in suspension. In the latter case it effects a 
kind of filtration. This phenomenon of imbibition may, in 
the case of solutions holding in suspension very finely 
divided molecules of solid matter, be very valuable for 
ascertaining the different properties of the blood according 
to its density. In fact, in certain maladies, its density and 
its viscidity are much diminished ; and in these cases serous 
infiltrations take place, as they do also, for the same reasons, 
after profuse sanguineous discharges. We shall hereafter 
find that alcohol, ether, water, &c., as well as aqueous sola- 



36 MOLECULAR ATTRACTION. LeCT. II. 

tions, when introduced into the stomach of living animals, 
disappear, but in unequal intervals of time, oil remaining 
there for a very long period. 

Believing that it would be of importance to compare 
alcohol at 36° Baume [sp. gr. 0-844] with distilled water, 
I provided myself with tubes filled with sand, pounded 
glass and sawdust, and here are the elevations that I ob- 
tained. 



Tube with Sand. 


Tube with pounded Glass. 


Tube with Sawdust. 


Alcohol, 85 millim. 
Water, 175 — 


175 millim. 

182 — 


125 millim. 
60 — 



Thus we see clearly that with either sand or pounded 
glass alcohol rises less than water ; a fact which is in ac- 
cordance with that which happens with capillary tubes. 

In another experiment I plunged into the same liquid, 
namely water, two tubes, both holding pounded glass, but 
the one containing twice as much as the other ; conse- 
quently the powder was finer in the first tube. The follow- 
ing were the results obtained : — 

In the first tube the liquid rose to 170 millimetres, in the 
second to 107 millimetres only in the same period. 

It is not easy to give an explanation of the relation ex- 
isting between the elevations in these two tubes. It is, 
however, natural to suppose that the liquid should rise 
more in the tube which contains double the quantity of 
matter, if we reflect on the augmentation of the solid sur- 
face which attracts the liquid, and on the smaller diameter 
of the capillary cavities. 

This phenomenon of imbibition is continually witnessed 
in a great number of instances in the tissues of animals and 



LeCT. II. IMBIBITION MODIFIED BY TEMPERATURE. 37 

vegetables. The latter, from being abundantly furnished 
with small spaces and capillary tubes, imbibe with the 
greatest facility, and absorb solutions with which they are 
placed in contact. This also is the case with the cellular 
tissue and the parenchyma of the lungs ; but the opposite 
effect takes place with the epidermis. 

Imbibitio7i modified by Temperature — I have likewise 
sought for some difference in the phenomena of imbibition 
at different temperatures. Two tubes prepared with sand 
were plunged into water, the one at a temperature of + 55° 
centig. [= 13PF.,] the other at + 15° centig. [= 59° F.,] 
and the results obtained were as follows : — 





Elevation after 70 seconds. 


Elevation after 11 minutes 


Tube at + 55° centig. 
at +15 — 


10 millim. 
6 — 


175 millim. 
12 — 



The influence of temperature on imbibition is, therefore, 
very considerable. Kow we know that in animals absorp- 
tion either by the skin, or in the interior of the economy, is 
more active in proportion as the liquid is warmer. 

Imbibition in different hydrometric Conditions of the Air. — 
I satisfied myself that imbibition was equal in air saturated 
with moisture and in dry air. 

Imbibition at different Degrees of atmospheric Pressure. — 
Another result, not less singular, is observed when we study 
imbibition by sand, ashes, and sawdust, in the vacuum of 
the air-pump, and in air at ordinary pressure. No differ- 
ence is perceptible in the height of the column of water at 
the end of ten minutes ; but in the experiment with sand, 
this peculiarity was observed, that for the first few minutes 



38 MOLECULAR ATTRACTION. LecT. II. 

the rise of the liquid was more rapid in the tube placed in 
a vacuum than in one which was contained in the air. 

Imbibition limited. — It may be asked whether, by the 
action of imbibition, a liquid can rise to an unlimited height. 
It would at first sight appear, that a column of sand, of ashes, 
or other pulverized bodies, one end of which is immersed 
in a liquid constantly maintained at the same level, should, 
by the force of imbibition, elevate the liquid to any height 
till the whole column has imbibed. Indeed, if we con- 
sider separately the action of each of the layers forming 
the column, we may suppose that after the imbibition of 
the first layer in contact with the liquid, the particles of the 
second layer immediately above wall deprive the first of a 
portion of its water, and the latter will re-obtain from the 
liquid mass the amount it had lost. By repeating this rea- 
soning for all the successive layers of the column, we 
arrive at the conclusion that each takes up the same amount 
of liquid as if it had acted separately, and thus, if the level 
of the liquid be kept constantly at the same height, the en- 
tire column, however long it may be, will imbibe. But 
experience does not confirm this re'asoning ; the liquid 
rises at first rapidly, then the ascending movement slackens, 
and at a certain height the liquid remains stationary. This 
fact cannot be ascribed to the evaporation in the upper 
layers of the column; for water rises to the same height 
in a column of sand, whether it be surrounded by the va- 
pour of water, or by dry air. I can only account for it by 
admitting the existence of small canals in the whole length 
of the column of powder, and then, consequently, capillary 
action, as well as the adhesion of the liquid to the surface 
of the grains of sand, will intervene. 

Agency of Imbibition in living Beings. — It is impossible 
not to perceive that imbibition plays an important part in 



Lect. II. 



HALES'S APPARATUS. 



39 



Fig. 1. 



the action of the juices of plants, as well as in the pheno- 
mena of the capillary circulation of the blood in animals. 
In another lecture we shall show that all the parts of living 
plants and animals soon become impreg- 
nated with a saline solution into which 
some part of them is immersed, and that 
its presence is easily recognised by tests. 
It will be sufficient for me to refer to the 
experiments of Hales and the more recent 
ones of Boucherie. The latter saw a pop- 
lar 28 metres [nearly 92 feet] in height 
absorb by its trunk, in 6 days, the enor- 
mous quantity of 3 hectolitres [about 66 
imperial gallons] of a solution of pyrolig- 
nite of iron. 

Halesh Experiments. — I shall here no- 
tice the experiments of Hales, made with 
the view of measuring what he calls the 
force of aspiration* of powders and of the 
stems of trees. 

[This experimenter filled a glass tube, 
c. r, i, 3 feet long, and J of an inch dia- 
meter [Jig. 1.,) with well dried and sifted 
wood ashes, pressing them close with a 
rammer. " I tied," he observes, " a piece 
of linen over the end of the tube at i, to 
keep the ashes from falling out. I then 
cemented the tube c fast at r, to the aqueo- 
mercurial guage, r z; and when I had filled the guage 
full of water, I immersed it in the cistern of mercury, x ; 



Hales's Apparatus for 
ascertaining the force 
with, which powders 
imbibe moisture. 



* I cannot find the terra ^^ force of aspiration" in Hales's Vegetable 
Statics. The phrases which Hales employs are, " the force with which 
trees imbibe moisture^" and '■Hhe imbibing power.'''' — J. P. 



40 



MOLECULAR ATTRACTION. 



Lect. II. 




Hales's Apparatus' for ascertaining 
the force with which plants imbibe 
moisture. 

b, the branch. 

r, c, z, the aqueo-mercurial guage. 

i, end of branch from which air 
escapes. 

I, the cistern of mercury. 



then to the upper end of the 
tube c, at o, I screwed on the 
mercurial guage, a, b. 

" The ashes, as they imbibed 
the water, drew the mercury 
up 3 or 4 inches, in a few 
hours, towards z; but the three 
following days it rose but 1 inch, 
J inch, and J, and so less. and 
less, so that in 5 or 6 days it 
ceased rising. The highest it 
rose, was 7 inches, which was 
equal to raising water 8 feet." 

In another experiment Hales 
substituted a tube 8 feet long, 
and ^ inch diameter, filled with 
red lead, for the tube contain- 
ing wood ashes, and obtained 
therewith a rise of 8 inches of 
mercury.*] 

If we substitute the branch 
of a tree for the tube filled with 
wood ashes, [as in fig. 2,] the 
mercury rises, as in the pre- 
ceding experiments made with 
powders. Hales regarded this 
phenomenon as dependent on 
a force which he terms " the 
force of aspiration."! 

Here are some experiments 



* That portion of the text enclosed between brackets has been intro- 
duced as a substitute for the less precise statement of Matteucci. I have 
employed the language of Hales, and have added his figures. — J. P. 

t See foot-note, p. 39. 



LeCT. II. HALES'S APPARATUS. 41 

which explain these facts in a simple and satisfactory man- 
ner. It is easy to show that the ascension of mercury takes 
place equally in two tubes prepared in the manner of Hales, 
but differing from each other in this, that in one of them the 
tube containing the ashes is open at the top, while in the 
other it is closed. 

It must, however, be observed, that the experiment 
would not be attended with this result if the column of 
ashes were short, or the latter less up-heaped. With an 
apparatus similar to that of Hales I made the following ob- 
servations. I luted a leaden tube to the top of a glass one 
containing the pulverised substance. By the aid of this I 
could easily remove the air from above the ashes. At the 
moment when the quicksilver began to rise I produced a 
vacuum, and the mercurial column not only did not de- 
scend, but it continued to ascend. It is, then, indubitable 
that the ashes form, above the column of water, a wall or 
partition which performs the office of a closed tube ; in fact 
Hales's apparatus is a barometer. In another experiment, 
at the moment when the mercury began to rise, I covered 
the whole with a bell-glass, and produced a vacuum ; the 
mercury instantly fell. I have obtained the same results by 
substituting a stem with leaves for the tube filled with ashes. 
If I introduce the upper part of this stem into a balloon, as 
I remove the air the mercury continues to rise, but on the 
contrary, if I form a vacuum over the mercurial reservoir, 
it immediately falls. Hence, then, we conclude that wRat 
Hales calls the force of aspiration (imbibition) is a simple 
barometrical phenomenon. Whether the column of ashes 
or the leaves and trunk of a tree form the upper closed part 
of the barometer, the water penetrates the powders or vege- 
table tissues by imbibition, and the atmospheric pressure 
gradually effects the rise of the liquid. 

Exhalation by Leaves. — We must, however, remark a 



42 MOLECULAR ATTRACTION. LeCT. IL 

very curious fact, which takes place when we employ a 
branch with leaves as in all the other experiments of Hales; 
it is, that the column of water continues to ascend ; so that 
we are forced to conclude that the vapour of water is ex- 
haled by the leaves, without these ceasing to act as the 
accurately closed wall of a barometer. It would appear 
that Magnus has obtained a like result by closing, with a 
piece of membrane, the upper part of the tube. From w^hat 
we have said, the ascension of the column of water should 
go on, but it is probable that the phenomenon becomes at 
first less manifest, and then completely ceases on account 
of the disorganization which occurs both in the membrane 
and the leaves. 

Chemical Effects produced by Capillary Forces. — I shall 
not leave this subject without mentioning to you some ex- 
periments tried with the view of producing by the mere 
operation of capillary forces and molecular attraction the 
effects of chemical affinity. If we reflect that any kind of 
liquid constantly ascends to the same height in a capillary 
tube ; that during imbibition more or less heat is produced^ 
as the experiments of Pouillet have demonstrated ; that, 
moreover, according to Becquerel, there is a disengage- 
ment of electricity; and, lastly, that capillary attraction is 
exerted at very minute distances only, and between the 
molecules of bodies ; we cannot deny that this force com- 
bines the principal characters of chemical affinity. We 
know the experiment of Doebeireiner, that if a mixture of 
water and alcohol contained in a bladder be exposed to the 
air, water constantly escapes from the mixture. In this 
case the water is imbibed by the membrane more readily 
than the alcohol, and is dissipated by evaporation. 

Salt Water made fresh by Filtration. — Another and more 
conclusive fact is mentioned by Berzelius : a saline solution 
filtering through a long tube filled with sand runs out more 



LeCT. II. SALT WATER MADE FRESH BY FILTRATION. 43 

or less, completely deprived of salt. I have confirmed this 
experiment by using a tube of about 8 metres [about 26 feet] 
long, filled with sand, and I have found that the density of 
the liquid, introduced by the upper aperture of the tube, was 
to that of the liquid escaping from the other end, as 1 : 0-91. 
But it is necessary to state that this difference of density 
was not always maintained ; after a certain time, the saline 
solution is as dense at its exit from the tube as at its en- 
trance. This proves that the decomposition of the saline 
solution takes place in the first action of contact between it 
and the particles of sand.* 

I have obtained an inverse result by employing a solution 
of carbonate of soda, which I caused to pass through a tube 
3 metres [nearly 10 feet] long, filled with sand. The den- 
sity of the liquid at its exit was to that at its entrance as 
1-005:1. 

The phenomena we have just referred to are very impor- 
tant on account of the applications that can be made of 
them to some of the functions of living beings which are 
not completely explicable by the mere action of capillarity 
and molecular attraction. 

* The facts here mentioned respecting the alteration in the density of 
a saline solution by filtration are very interesting. They are susceptible 
of numerous applications in geology. For example, the marine origin of 
fresh- water springs has hitherto been deemed impossible, " because," as a 
recent writer observes, " sea water cannot be freed from its salt by filtra. 
tion." Matteucci's experiments demonstrate the possibility of this ori- 
gin.— J. P. 



44 ENDOSMOSE. LecT. III. 



LECTURE III. 



ENDOSMOSE. 



Argument. — Endosmose and Exosmose ; explanation of the terms ; Du- 
trochet's endosmometer; membranes and other solids through which 
endosmose takes place ; liquids which effect it ; velocity and intensity 
of the current; its direction affected by the density and temperature of 
the liquid ; its force. Theory of endosmose. Endosmose of organized 
cells. Malteucci and Cima's experiments; double -action endosmome- 
ter; arrangement of the membranes used in three classes. 

Class 1. — Skins of the torpedo, frog, and eel ; influence on the current — 
of the direction of the surface of the skins — of their fresh or dried 
state — of the skin of different regions — and of the nature of the liquid. 

Class 2. — Mucous membrane of the stomachs of the lamb, dog, and cat, 
and of the gizzard of the fowl ; influence on the current — of the 
direction of the surface of the membrane — and of the nature of the 
liquid. 

Class 3. — Mucous membrane of the bladders of the ox and pig ; influence 
on the current — of the direction of the surface of the membrane — of 
its fresh, dried, and putrid state — and of the nature of the liquid. 

General conclusions. 

Dutrochet's explanation of exosmose stated and objected to. 

Physiological applications; the current is promoted, in skins, in the 
direction towards the secreting surface ; relation of this phenomenon 
to secretion ; absorption from mucous membranes ; nutrition of ovules 
of Mammalia, and opening of the sperm-sacs of the Cephalopoda^ 
effected by endosmose; endosmose of organized cells; endosmotic action 
of purgatives ; endosmose of liquids in motion ; remarkable influence 
of hydrochlorate of morphia on endosmose. 

Having considered the phenomena of capillary attraction 
and imbibition, it becomes necessary, in order that you 
may be enabled to apply your knowledge of these subjects 
to the functions of exhalation and absorption, that I should 



LeCT. III. ENDOSMOSE. 45 

make you acquainted -with another phenomenon, which, 
although exclusively within the domain of physics, yet 
nevertheless, by the physiological applications of w^hich it 
is susceptible, is really connected with the study of or- 
ganized beings. I refer now to the phenomenon discovered 
by Dutrochet,* and termed by him endosmose. It is the 
mutual action of two liquids on each other when separated 
by a membrane. Although its theory is not yet completely 
known, the subject is nevertheless of the highest impor- 
tance. 

I shall commence by explaining to you the fundamental 
fact in its simplest form. Here is a glass tube whose 
lower extremity, closed by a piece of bladder, is expanded 
into the form of a funnel. This instrument is called an 
endosmometer. 

If we pour into it an aqueous solution of either gum or 
sugar, and then immerse the closed extremity in pure 
water, we shall find that, notwithstanding the excess of 

* Dutrochel's firj-t memoir on endosmose and exosmose was read to the 
Academic Royale des Sciences, on the 23d of July, 1827 (see the Ann. de 
Chim. et de Phys. torn, xxxvii. p. 393. 1827.) 

Ten years previously, my friend Mr. Porrett, the present treasurer of 
the Chemical Society of London, had communicated to the editor of the 
Annals of Philosophy (vol. viii. p. 74, for July, 1816) a paper on two 
^^ curious galvanic experiments,''^ ore of which was the production of en- 
dosemose between two liquids separated by a membrane and subjected 
to the action of voltaic electricity. He called the phenomenon, electro- 
JiltrQtion ; RTid hsks, whether jointly with electro-chemical action, it is 
not " in constant operation in the minute vessels and pores of the animal 
system." 

M. Parrot, of St. Petersburgh, lias' recently presented to the Academie 
Royale des Sciences, an inaugural dissertation, published in 1803, giving 
an account of the phenomena presented by two liquids of unequal density, 
separated by a permeable organic diaphragm, and pointing out their ap- 
plications to physiology and pathology. {Comptes rendus^ torn. xix. pp. 
607. 619. for Sept. 23d. 1844.)— J. P. 



46 



ENDOSMOSE. 



Lect. III. 



pressure exercised by the solution, the water continually 
Fig. 3. passes into the tube by liltration through the 
membrane. The liquid within becomes thus 
elevated to a certain extent, and may even 
flow over by the upper aperture. At the 
same time, a certain quantity of the mucila- 
ginous or saccharine liquid escapes from the 
tube through the bladder, and mixes with the 
water ; but the quantity is necessarily less than 
that of the water which passed in the oppo- 
site direction through the membrane. Dutro- 
chet has called the first of these phenomena 
endosmosey and the second exosmose. 

Endosmose through Membranes, ^c. — Mem- 
branes produce endosmose until they begin to 
putrefy, when the phenomenon ceases, and 
the liquid which had risen into the tube, de- 
scends and filters through the membrane. 
It is not membranes only which are en- 
dowed with this property : very thin plates of slate, or bet- 
ter still of baked clay, produce the same effect, though in 
a more feeble degree. Calcareous and siliceous laminae, 
on the contrary, have no effect of the kind : with them en- 
dosmose does not take place. 

Intensity of the Current. — The nature of the liquid em- 
ployed greatly influences the phenomenon. Endosmose 
is more obvious in proportion as the density of the liquid 
in the tube exceeds that of the exterior liquid. It might 
seem that the intensity of the current is proportional to 
the difference of the densities of the two liquids ; but alco- 
hol, which is lighter than water, causes, when introduced 
into the tube, endosmose of the water which is placed ex- 
terior to it. Saline solutions produce, through membranes, 
very energetic, but less durable effects. 



Endosmometer. 



LeCT. III. VELOCITY OF THE CURRENT. 47 

Increase of temperature augments the rapidity of the cur- 
rent of endosmose. 

Dutrochet found that the slightest trace of sulphuretted 
hydrogen destroyed endosmose. It is probable, however, 
that this eflfect arose from the alteration in the condition 
of the membrane when it commences to evolve this gas ; 
for fresh membrane placed in contact with sulphuretted hy- 
drogen is very active. 

Velocity of the Current. — Dutrochet endeavoured to 
measure the velocity with which a liquid passes, by virtue 
of endosmose, from the exterior to the interior of the tube. 
Here are the results of his experiments : — With a mem- 
brane of 40 millimetres in diameter, and a tube of 2 milli- 
metres, a solution of sugar, whose density was 1*145 rose 
34 divisions in the space of an hour and a half; each 
division being 2 millimetres. In another experiment, he 
employed a solution of sugar, the density of which w^as 
1-228, and the ascent in the same space of time was 53 
divisions. Lastly, in a third experiment, with a solution 
of sugar of the density of 1*083, the column mounted 19| 
divisions in the same interval of time. It is evident, 
therefore, that the velocity of endosmose is proportional 
to the excess of density of the interior liquid over that of 
the water employed as the exterior liquid. 

Dutrochet took different solutions having the same densi- 
ty, and compared them with water, from which they were* 
separated by bladder. 

The following ratios express the variable intensity of en- 
dosmose obtained in the different cases : — 



48 • ENDOSMOSE. LeCT. III. 

Intensity of Endosmose of various Liquids with Water, 

(Dutrochet.) 

Solution of gelatine . - . 3 

" gum - - - - 5-17 

" sugar - - - - 11 

" albumen - - - - 12. 

From this table we see, that of all organic substances 
soluble in water, albumen produces endosmose with the 
greatest force. 

Direction of the Current. — Among the most curious facts 
discovered by Dutrochet, while studying endosmose, must 
be mentioned that of the variation in the direction of the cur- 
rent between certain acid solutions and w^ater, according 
to their density and temperature. This is especially mani- 
fested by a solution of hydrochloric acid. Thus, with hy- 
drochloric acid at the density of 1*02, endosmose takes 
place from the w^ater to the acid, whilst at the density of 
1-015, the current is in the opposite direction; that is to 
say, it is from the acid to the water. 

Force of the Current. — Dutrochet endeavoured to deter- 
mine the amount of pressure exercised by the column of 
liquid elevated by endosmose in the different cases. For 
this purpose he employed the apparatus which Hales first, 
and afterwards Mirbel and Chevreul, used for measuring 
the pressure of the juices in plants. In this apparatus the 
pressure is estimated by the height of a column of mercury 
raised by the liquid. 

In studying endosmose under this point of view, Du- 
trochet proved that, all other things being equal, the force, 
which produces the current of endosmose, is proportional 
to the excess of the density of the interior liquid over that 
of the water. We have already seen that the velocity of 
endosmose likewise varies. It, therefore, follows, that 



LeCT. III. THEORY OF ENDOSMOSE. 49 

assuming this law to be true in all cases, syrup, whose 
density is 1*3, produces a current capable of raising a 
column of mercury of 127 inches (3 metres 42 centimetres,) 
or what amounts to the same thing, equal to the enormous 
pressure of 4| atmospheres. 

Theory of Endosmose. — Dutrochet has endeavoured to 
give an explanation of the phenomena of endosmose ; and 
Poisson and Becquerel have proposed others. Thus, some 
ascribe endosmose to the action of an electric current de- 
veloped by the contact of the two different liquids ; — a cur- 
rent which will produce the passage of the water through 
the membrane, from the positive to the negative pole, as in 
the well-known experiment of Porret. But to render this 
explanation probable, it would be necessary to prove that 
the contact of water with alcohol, solution of sugar, &c., 
developes electricity ; which is not the case. Poisson sup- 
posed that the least dense liquid entered the capillary tubes 
of the membrane, and that this capillary thread, drawn 
down by the pure water, and up by the denser liquid, must 
be elevated in virtue of molecular attraction. But this ex- 
planation becomes inadmissible when we consider that al- 
cohol, which is lighter than water, produces endosmose ; 
and that certain calcareous and siliceous stones, placed un- 
der the same conditions as membranes and plates of clay, 
do not give rise to the same effect. 

Up to the present time we have not any satisfactory theory 
of endosmose; but we know that the general conditions of 
the phenomena are as follow : — 

1st. That the two liquids should have an affinity for the 
interposed membrane. 

2dly. That the two liquids should have an affinity for 
each other, and be miscible. 

If one of these conditions be wanting, endosmose does 
not take place. Experiment proves that the current of en- 
4 



50 ENDOSMOSE. LeCT. III. 

dosmose is not produced by the least dense liquid, nor by 
the most viscid one, nor by that which is endowed with the 
greatest force of ascent in capillary tubes. The current is 
in general determined by the liquid which has the greatest 
affinity for the interposed substance, and by w'hich it is 
imbibed with the greatest rapidity. In fact it is evident 
that the membrane imbibes the two liquids unequally ; and 
that the one which is imbibed with the greatest facility, 
ought to mix with, and augment the volume of, the other. 

Endosmose in Living Beings. — What we have here stated 
must be sufficient to convince you that this phenomenon is 
perhaps one of the most important physical facts applicable 
to the functions of living beings. Microscopic observation 
has now put beyond doubt that, in all tissues, whether 
vegetable or animal, and in those liquids which are pro- 
duced by the alteration of organized and living beings, there 
are constantly found, at a certain epoch, microscopic cor- 
puscles, which have a peculiar and characteristic form, and 
are called elementary or primitive cells. These bodies 
consist of an exceedingly delicate membrane, which has a 
spherical form, encloses a liquid, and has on its inner side 
a small organized body, called the nucleus or cyto-hlast. 
The cells float at first in a liquid, which Schwann has named 
cyto-blastema, and they ultimately become included in, and 
almost confounded with it, when this liquid acquires a 
greater or less density. In different tissues, the elementary 
cells are more or less closely approximated to each other ; 
the cytO'blastema^ or intercellular substance, being invariably 
the bond of union between them. The life of the elemen- 
tary cells certainly plays the most essential part in the de- 
velopment and preservation of the tissues of living bodies; 
and, since these cells are found under conditions favourable 
to endosmose, we have no reason for refusing to admit its 
existence. A vesicle filled with a liquid, and placed in the 



LeCT. III. APPARATUS. 51 

midst of another liqurd, may act on the outer one, receive 
the surrounding liquor, and reject the one it had previously 
contained, by operating in a manner analogous to endos- 
mose. 

Matteucci and Cima^s Experimetits. — We must, however, 
confess that hitherto very few investigations have been 
undertaken with the view of making such applications of 
endosmose to physiology as the subject appears to be sus- 
ceptible of. To do this it was necessary to vary the liquids 
between which endosmose takes place, and to select the 
membranes, so that we might always keep as close as pos- 
sible to the conditions under which the analogies, between 
this phenomenon and those which exist in the interior of 
living bodies, have been observed. In conjunction with 
Professor Cima I undertook this inquiry, and I shall now 
state the results of our researches. 

Classes of Membranes. — The membranes which we sub- 
mitted to experiment may be arranged in three classes; the 
first including the skin of the frog, the torpedo, and the eel ; 
the second, the stomach of the lamb, the cat, and the dog, 
and the gizzard of the fowl ; and the third, the bladder of 
the ox and of the pig. 

Apparatus. — We shall not stop to describe our apparatus, 
as it differed in no way from the endosmometer of Dutrochet. 
But I may observe that in all our experiments we used, at 
the same time, two endosmometers, the bore of whose tubes 
was exactly three millimetres [about ith of an English inch] 
in diameter ; and their scale was divided into millimetres. 
In a glass vessel, sufficiently large to hold the two instru- 
ments, we placed a support upon which was firmly fixed a 
metallic plate perforated with a great number of small aper- 
tures. Upon this plate we put the two endosmometers ; 
and in order that they might not be liable to a change of 
position, we loaded them with a large leaden plate pierced 



52 ENDOSMOSE. LeCT. III. 

with two holes, w^hose diameter was equal to that of the neck 
of the instruments. 

In the course of the experiments, the interposed mem- 
brane in one of the endosraometers w^as placed in the re- 
verse position to that of the other: for example, if made of 
skin, it was so placed that, in one case, the external surface 
was directed towards the interior of the instrument, whilst, 
in the other, the internal surface was turned in this direc- 
tion. 

AH the experiments were made at a temperature of from 
+ 12^ to + 15° centigr. [=;, 53-6^ Fahr. to 59°.] In the 
greater number of cases they lasted for two hours, and were 
repeated several times. We took care to provide the two 
epdosmometers employed in the comparative experiments, 
wuth two portions of membrane of equal si:5e taken from the 
same animal, and from two symmetrical regions of the body 
or organ employed. The liquids used were, besides spring 
water, the following, of which we give, once for all, the 
density according to the degrees of Baume's areometer: — 

Density of the Liquids in the Endasmometrical Experiments. 





Baum6's Areometer. 


Specific Gravity. 


Solution of sugar 

white of egg - 
gum arable 

Alcohol 


19° 
34° 


1-1 5-3 

1-029 
1'036 

0-855 



These liquids were usually contained in the interior of 
the instruments, the water being placed externally. 

In some particular instances we altered the arrangements 
of the liquids and instruments, by employing a separate 
vessel for each endosmometer. We also used another in- 
strument, of which a figure and description are subjoined: 
B and c are two cylindrical brass receivers, ground into 



Lect. III. 



EXPERIMENTS. 



53 



each other; b has at a a brass plate perforated by holes, on 

which the membrane submitted to experiment is placed ; c 

is also furnished with ^. , 

Fig. 4. 
a plate perforated with 

holes, which, when the 
two cylinders b c are 
united, as in the sub- 
joined figure, fits accu- 
rately on the membrane, 
which is thus pressed be- 
tween the two plates. In 
this condition it can only 
yield to the greater pres- 
sure exercised upon it by 
a liquid, denser than that 
contained in the other 
portion of the cylinder. 
mn, p are two tubes of 
equal calibre : the first 
communicates with the 
receiver b ; the other, 
with the receiver c. When we wish to use the instrument 
we introduce the denser liquid into b, and fill the tube m n, 
with it to a certain height, c is then filled with water by 
plunging it in a vessel of this liquid. The two cylinders 
are then fitted together under water, and the two receivers 
pressed together by a vice, in order that the liquid con- 
tained in c may not escape through the fissure of the join- 
ing. We place the instrument on a level, and then put the 
two liquids at 0° of the scale s. With this instrument we 
obtain at the same time the value both of the elevation and 
of the depression of the two liquids, which gives a great 
precision and much experimental facility, by thus doubling 
the results. 




Double-action Endosmometer. 



54 ENDOSMOSE. LeCT. III. 

Class 1. Experiments with the Skins of the Frog, Tor- 
pedo, and Eel. — I shall first state the results obtained by 
employing, as the membranes, the skins of frogs, torpe- 
does, and eels, with the before-mentioned solutions for the 
liquids. 

Influence of the Position of the Membrane. — In our first 
trial we noticed, in a very clear manner, the marked in- 
fluence exercised upon the phenomenon of endosmose by 
the position of the interposed membrane. It was in fact 
this first discovery which led us to examine, in this point of 
view, the effects produced by the bladder and stomach of 
divers animals. With some trouble we obtained entire 
skins, and deprived them of all adherent sub-cutaneous 
cellular tissue. After having thus prepared them, we cut 
off those parts which, in the torpedo and eel, are perforated 
by the cutaneous appendages, and so obtained membranes 
well fitted for our experiments. 

Skin of the Torpedo. — By employing the skin of the tor- 
pedo, placed in one endosmometer with its external sur- 
face towards the interior of the instrument, and in the other 
reversely, and by filling the two endosmometers with a solu- 
tion of gum Arabic, we observed that, whilst the liquid in 
the first instrument rose 30 millimetres, it rose in the second 
sometimes 18, and sometimes only 6 millimetres. In certain 
cases we saw the liquid elevated 20 millimetres or more, in 
the first tube, whilst it scarcely rose at all in the second. 

These differences are equally observed, with a solution 
of sugar. Thus, this liquid which rises 30 and even 80 
millimetres when the external surface of the skin is turned 
towards the instrument where the liquid is contained, rises 
at the utmost only 2 millimetres when the membrane is 
placed in the contrary direction. In one case where the 
first-named arrangement was adopted, the liquid rose 80 



LeCT. III. EEL SKINS. 55 

millimetres; but reached only 20 millimetres \yhen the se- 
cond arrangement was resorted to. 

With albuminous solutions the elevation was 26 milli- 
metres when the external surface of the skin was in contact 
with it, and 13 millimetres when placed in the contrary 
direction. 

Skin of the Frog. — The results obtained with the skin of 
the frog, agree in general with those furnished by the skin 
of the torpedo. We remarked that the direction of the en- 
dosmotic current was constant, and was from the water to 
solution of sugar, or of gum, or of albumen* We observed 
that the membrane possessed the property of rendering en- 
dosmose more or less intense, according to its position rela- 
tively to the two liquids. In arranging the skin of the frog 
in the two endosmometers in the usual manner, we obtained 
an elevation of 36 millimetres when the external surface 
was in contact with the solution of sugar, and of 24 milli- 
metres in the reverse arrangement. In several cases the 
former was exactly double the latter. There was likewise 
a very marked difference, and always of the same kind, 
when we used solutions of albumen and of gum Arabic. 
With the first there was an elevation of 24 millimetres, 
with the second 32 millimetres, when the external surface 
of the skin was in contact with them; whilst there was only 
12 millimetres for a solution of albumen, and 16 millimetres 
for a solution of gum, when the internal surface was turned 
towards them. 

Eel Skins. — The differences which we have already re- 
marked from using a solution of sugar and skins of frogs 
and the torpedo, exist equally in the case of the eel skin. 
But what is singular with the latter is, that the difference is 
not manifested at the commencement of the experiment. 
At first the elevation of the liquid is alike in both instru- 
ments ; but after a lapse of two hours we perceive that, in 



56 ENDOSMOSE LeCT. III. 

the endosmpmeter in which the external surface of the skin 
is turned tovvards the solution of sugar, the elevation is 30 
millimetres, while in the other instrument it is only 20 
millimetres. With an albuminous solution and gum water, 
the differences observed from the commencement of the 
experiment are the same as those which usually take place ; 
and, although we ultimately find the albuminous solution 
rises 8 millimetres, and the solution of gum rises 20 milli- 
metres, w^hen the external surface of the skin is turned 
towards the liquid ; we observe, on the contrary, that when 
the position of the skin is reversed, the albuminous solution 
rises only 4 millimetres, and the solution of gum 17 milli- 
metres. 

The fresh condition seems more necessary for the skin of 
the eel, than for that of the frog and torpedo, when we wish 
to mark the difference in the elevation of the liquids con- 
tained in the endosmometers. If the skin of the eel has 
been removed from the animal for one or two days, no dif- 
ference is observed between the two positions of the mem- 
brane; and the solutions of sugar, albumen, and gum 
respectively rise, in the same space of time, to an equal 
extent in both instruments. 

Endosmose between Mcohol and Water. — By employing 
water and alcohol, Dutrochet obtained the current in the 
direction from the former to the latter. This consequently 
formed an exception to all the other cases, in which he found 
that the direction of the current was from the least to the 
most dense liquid. 

The influence of the position of the skin, employed as 
the membrane interposed between these two liquids, has 
been rendered evident by our experiments ; but the position 
favourable to the current, which is constantly from the water 
towards the alcohol, is not the same for the three kinds of 
skins alluded to. Thus, when we use the skin of the frog. 



LeCT. III. BETWEEN ALCOHOL AND WATER. 57 

the current is promoted from the external to the internal 
surface, by being directed always from the water to the 
alcohol. In various and frequently repeated experiments, 
we have observed an elevation of 20, 24, and 40 millime- 
tres when the internal surface of the skin was placed towards 
the alcohol, whilst in the reverse position the corresponding 
elevations were only 4, 12, and 20 millimetres. Under 
analogous circumstances, the position of the membrane 
being favourable, the elevation was 28 millimetres ; in the 
other position, on the contrary, there was no elevation. 
With the skin of the eel the reverse takes place. With this 
the current is favoured from the internal to the external sur- 
face ; and whilst the alcohol contained in the instrument 
rises to the height of 20 millimetres, when in contact with 
the external surface of the skin, it only rises to 10 millime- 
tres when the position is reversed. 

This difference of elevation always takes place in the 
same direction, and is confirmed for the eel-skin, as for the 
skin of the torpedo. The elevation has been at 50 milli- 
metres in one instrument, and 20 in the other. 

Some anomalies which we observed in our earliest trials, 
led us to study, with greater precision, the circumstances 
under which endosmose takes place through the skin of the 
torpedo, when interposed between water and alcohol. We 
constantly found these difTerences when the skin of the tor- 
pedo was fresh, and had not been used for previous experi- 
ments, but it continued only during the first hour of the 
experiment or a little after. The elevations subsequently 
follow a different law, and the height in the endosmometer, 
when the external surface of the skin is in contact w4th the 
water, goes on diminishing, afterwards ceases, and ultimate- 
ly the direction of the current changes. 

Out of the numerous experiments which we have tried, 
Ave select the following, in which we have marked the ele- 



58 



ENDOSMOSE. 



Lect. III. 



vations hour by hour. We shall call the endosmometer, 
in which the interior surface of the membrane was in con- 
tact with the water, A; and the one in which this surface is 
towards the interior of the instrument, B. 

Endosmose through the S/dn of the Torpedo. 



Endosmometer A. 

Internal surface of the membrane 

towards the water. 


Endosmometer B. 

Internal surface of the membrane 

towards the alcohol. 


Milli- 
metres. 
Elevation during the 1st hour 23 
« 2d « 25 
" 3d " 25 
" 4th « 25 


Milli- 
metres. 
Elevation during the 1st hour 17 
" " « 2d " 3 
" « " 3d " 
Depression in the 4th " 3 



Conclusions. — We conclude, therefore, 

1st. That so long as the skin of the torpedo is fresh, en- 
dosmose takes place in the usual manner, from the water 
to the alcohol ; but invariably with this difference, that, 
whilst the internal surface of the skin is in contact with the 
water, the elevation is as 3, and, in the reverse position, 
as 2. 

2dly. That while in the first position of the membrane 
A, the force of endosmose remains constant for several 
hours ; in the second position B, the same force diminishes, 
and after some time is extinguished. 

3dly. That, after a certain time, the direction of the 
current changes, and is then from the alcohol to the water, 
when the internal surface of the skin is turned towards the 
alcohol; whilst it remains constant in the contrary position 
of the skin. 

We think that we ought to ascribe these peculiarities with 
alcohol, to the chemical action which this liquid exercises 



Lect III. 



SKIN OF DIFFERENT REGIONS. 



59 



upon the substance of the membrane, and to the consecu- 
tive alteration of structure. 

The diminution of the intensity of endosmose observed 
with the skin of the torpedo, but only in the less favourable 
position of the membrane, is confirmed, whatever may be 
its position, by employing the skin of the frog; but this 
decrease does not proceed regularly, as we may observe in 
the following table, in which A and B represent the same 
endosmometers as in the preceding table : — 



Endosmose through the Skin of the Frog. 



Endosmometer A. 

Internal surface of the membrane 

towards the water. 


Endosmometer B. 

Internal surface of the membrane 

towards the alcohol. 


Milli- 
metres. 
Elevation during the 1st hour 23 
« u 2d « 40 
" " « 3rd « 12 
" " " 4th " 22 

" « " 6th \ ^^ 


Milli- 
metres. 
Elevation during the 1st hour 30 
♦* 2d " 55 

" " 4th " 35 

" " 5th r, 53 

u « *t gth \ ^ 



During the night the liquid overflowed both the endos- 
mometers, but there was no inversion of the current, as 
had taken place with the skin of the torpedo. Neither 
was this phenomenon observed with the skin of the eel, 
even when the experiments were continued for more than- 
fifteen hours ; but the increments were irregular, as with 
the skin of the frog. 

Skin of different Regions. — It was important to determine 
whether the force of endosmose varied when the skin was 
taken' from different regions of the body. The experiments 
made to ascertain this were not very numerous ; and we 
shall content ourselves by saying that no diflference was 
observed in the current of endosmose, whether we used 



60 



ENDOSMOSE. 



Lect. hi. 



the skin which, in the torpedo, covers the electric organs, 
or that which covers the back ; and that we detected no 
difference by employing the skin of the belly or that of the 
back of the frog. 

Endosmose of different Liquids. — We undertook a long 
series of experiments to determine the respective forces of 
endosmose with different liquids, through the three skins 
above mentioned. For this purpose three endosmometers 
were simultaneously prepared ; one with the skin of the 
torpedo, a second with the skin of the frog, and a third 
with eel skin ; in all the cases the skins were placed with 
their external surface towards the interior of the instru- 
ment, which contained sometimes a solution of sugar or 
of albumen, sometimes gum water or alcohol. The en- 
dosmometers were plunged into a glass vessel filled with 
spring water : this arrangement presented the advantage 
of enabling us to observe immediately the difference in the 
height of the liquids when traversing the three kinds of 
skins. The following table shows the intensity of endos- 
mose of each of the liquids when traversing the different 
skins : — 

Relative Intensity of Endosmose through different Skins. 



Solution of sugar . 
" " albumen 

" " gum 

Alcohol 



Skin of Torpedo. Skin of Frog. Skin of Eel 



100 millim. 

30 " 
120 " 

35 " 



25 millim. 
15 « 
22 " 

80 " 



15 millim. 

8 " 

6 •» 

55 «' 



This table proves, 

1st. That with the skin of the torpedo the current of en- 
dosmose is strongest when we use a solution of sugar, of 
gum, or of albumen, for the internal liquid. 



Lect. III. 



STOMACH OF THE LAMB. 



61 



2dly. That with these same liquids it is less with the skin 
of the eel than with that of the frog. 

3dly. That we have a current of endosmose from water 
to alcohol, stronger with the skin of the frog than with the 
eel skin, and with the latter more energetic than with the 
skin of the torpedo. 

4thly. That this current through the skin of the frog still 
continues strongest from the water to alcohol, although the 
skin be not placed, with respect to the liquids, in the 
manner most favourable for the production of the pheno- 
menon. 

5thly. That the intensity of endosmose for the same skin 
varies for each liquid ; and for this reason, these liquids 
ought to be arranged for the different skins in the follow- 
ing order, commencing w^ith that which gives the strongest 
current, and proceeding to that which yields the weak- 
est : — 

Order of Intensity of different Liquids for different Skins. 



Skin of the Torpedo. 


Skin of the Frog. 


Skin of the Eel. 


Solution of gum 

•' sugar 
Alcohol 
Solution of albumen 


Alcohol 

Solution of sugar 
'* gum 
" albumen 


Alcohol 

Solution of sugar 
" aibumen 
" gum 



These later results prove, that the order in which Dutro- 
chet arranged these liquids, relatively to the intensity of 
endosmose which takes place between them and water, 
ought not to be considered as constant for every case. 

Class 2. Experiments with the Gastric Membrane of the 
Lamb, Bog, and Cat, and Gizzard of the Fowl. — We shall 
reserve our general conclusions from what we have now 



62 ENDOSMOSE. LeCT. III. 

stated, and pass on to the observations we have made when 
using membranes which we have placed in the second class; 
namely, the stomach of the lamb, the dog, and the cat, and 
the gizzard of the fowl. 

In all our experiments we carefully removed every por- 
tion of muscular fibre from these organs before applying 
them to the endosmometers ; so that we used the mucous 
membrane only. The greatest number of our experiments 
w^ere made with stomachs taken from these animals imme- 
diately after death : where it was otherw-ise, we shall men- 
tion it. 

Stomach of the Lamb, — In using the stomach of the lamb, 
prepared, as we have already stated, with a solution of sugar 
in the interior of the two endosmometers, and placing the 
membrane with its internal surface (namely, that which is 
naturally turned towards the interior of the cavity of the 
stomach) directed tow^ards the interior of the instrument, 
the elevation of the liquid was 56 millimetres in one case, 
and 54 in another ; but in the reverse position of the mem- 
brane it was 72 millimetres in the first, and Q>Q in the second. 
These two experiments lasted but one hour and a quarter; 
endosmose was then favoured by employing a solution of 
sugar, and was directed from the interior to the exterior of 
the stomach. 

The contrary takes place in making use of the solution 
of white of egg. When this liquid was in contact with the 
internal surface of the stomach, it rose in the instrument 
23, 28, and 35 millimetres in the space of two hours as 
usual. 

But when we introduced into the endosmometers a solu- 
tion of gum Arabic, the elevation in the two opposite po- 
sitions of the membrane was sometimes nothing, sometimes 
equal, and only 8 millimetres in the two instruments ; in 
some cases there was in one, 12 millimetres, when the in- 



LeCT. III. STOMACH OF THE CAT. 63 

ternal surface of the membrane was in contact with the gum 
solution ; and 8 millimetres, when the position was reversed. 
The intensity of the endosmose between the water and the 
gum solution is excessively weak when it is exerted through 
the mucous membrane of the stomach of the lamb ; and it 
is necessary, therefore, to prolong the experiment beyond 
the ordinary time, in order to obtain a sufficiently obvious 
elevation. Those we have now mentioned, were obtained 
after more than four hours experimenting. It must also be 
observed, that the current of endosmose through the mem- 
brane soon ceases when we employ the two liquids now 
referred to. Indeed, it often happens that the solution of 
gum, after having attained a slight elevation, does not ex- 
ceed this at the end of two hours, nor even by prolonging 
the experiment for many hours. 

The favourable position for endosmose between water 
and the solution of sugar, which we have observed when 
we use the stomach of the lamb, is not the same when we 
employ the stomach of the cat and the dog ; with the sto- 
mach of the cat, the elevation to which the solution of 
sugar reached in the tube of the instrument was either 30 
millimetres or 15 millimetres, according as the internal sur- 
face of the membrane was placed towards the interior o^ 
the instrument, or had the reverse position. With the sto- 
mach of the dog, the elevation was, in the jfirst case, 68 
millimetres, and, in the second, 8 millimetres. 

Stomach of the Cat. — With the stomach of the cat, en- 
dosmose from water to the solution of gum is also directed 
from the external to fhe internal surface of this organ. 
Thus, when the mucous surface of the membrane is in con- 
tact with gum water, the elevation reaches 38 millimetres, 
and when in the other position, only 14. This difference 
is observed only when the stomach is very fresh ; should 
the animal from which it has been taken, have been dead 



64 , ENDOSMOSE. LeCT. III. 

some time, we observe that, at the commencement of the 
experiment, there is a slight elevation sometimes equal in 
both instruments; sometimes greater, sometimes less, in 
the one than in the other; but the liquid soon descends. 
By changing the position of the liquids, that is to say, by 
putting the solution of gum outside, and the pure water 
within the instrument, the water descends. 

Stomach of the Bog. — The same phenomena were pro- 
duced when we employed the stomach of the dog. We 
have not made any experiments with the stomach of the 
latter animal immediately after its death, using for the in- 
ternal liquid an albuminous solution. The results which 
we have now explained were made several hours after the 
death of the animal. The albuminous solution rose to an 
equal height in the two instruments in four different experi- 
ments. In one of them, which we select from amongst the 
others, this elevation was 20 millimetres in one hour; and 
it did not vary for three hours more, in the endosmometer 
where the internal surface of the stomach was towards the 
interior of the instrument, whilst in the same interval of 
time it fell 25 millimetres in the other endosmometer. In 
general, it rarely occurred that the column remained sta- 
tionary in either of them. In most cases (we always refer 
to the membrane of the stomach of the dog when it is not 
fresh) the liquid descended in both instruments after having 
manifested a greater or less elevation ; but the diminution 
of height was double, and often treble, in the endosmo- 
meter in which the external surface of the membrane was 
turned towards the albuminous solution. By reversing the 
position of the liquids, and placing the solution of white of 
egg outside, and the water inside the endosmometers, we 
found that the internal Hquid descended equally in both. 
These depressions are caused by the cessation of endos- 
mose, in consequence of the alterations supervening in the 



I 

LeCT. III. GIZZARD OF THE FOWL. 1^5 

structure of the membrane some time after death ; but the 
influence of the position of the two surfaces continues, to a 
certain point, even in the altered membrane. We have, 
indeed, remarked that the fall of the albuminous solution is 
double, and even treble, in the endosmometer where the 
external surface of the membrane is towards the inner side 
of the instrument. 

Gizzard of the FowL-r-Wiih. the mucous membrane of 
the gizzard of the fowl, using a solution of sugar and pure 
water, endosmose is stronger from the external to the inter- 
nal surface of the membrane, though, in general, the differ- 
ence of the elevation between the liquids of the two endos- 
mometers is not very great. Thus, when the internal part 
of the membrane was towards the interior of the instrument, 
the elevation was 48 milHmetres, whilst it was 43 in the 
contrary position. It is not unusual to see in the first posi- 
tion a certain elevation, as of 17 millimetres, of 20 milli- 
metres, &c., whilst in the second the liquid remains un- 
moved. We ought also to mention the promptitude with 
which the current of endosmose from water to a solution of 
sugar ceases, through the gizzard of the fowl. Generally 
the liquid column becomes stationary in both tubes at the 
end of two hours at most. 

Endosmose between water and the albuminous solution 
through this membrane (the gizzard of the fowl) seems to 
take place indifferently, whatever be the position of the sur-* 
faces wdth reference to the two liquids. We have proved 
this fact several times. In a solitary instance we saw the 
liquid rise 15 millimetres in the endosmometer, where the 
internal surface of the membrane was towards the interior 
of the instrument, whilst the liquid in the other instrument 
only rose 5 millimetres. We obtained the same results 
with a solution of gum as with the albuminous solution. 
In both positions of the mucous membrane of the gizzard of 
5 



66 ENDOSMOSE. LeCT. Ill, 

the fowl, the elevation of the liquid was also the same, when 
we prolonged the experiment several hours. When, in 
some rare cases, we remarked a slight difference, at most 
of 1 or 2 millimetres, it was always in that endosmometer 
in which the inner surface of the membrane was in contact 
with the solution of gum. 

To complete our account of the results obtained by the 
employment of the membranes in this second class, it only 
remains for us to add the phenomena observed when we 
employed alcohol for the inner liquid, putting it succes- 
sively in contact with each of the surfaces of these mem- 
branes. With the stomachs of the lamb, the cat, and the 
dog, endosmose was invariably directed from the water to 
alcohol, and was promoted from the internal to the external 
surface of the membrane. Indeed, we have seen in the en- 
dosmometer where the external surface of the mucous mem- 
brane of the stomach of the lamb was turned towards the 
interior of the instrument which contained alcohol, the ele- 
vation attained 88 millimetres, and only 10 millimetres in 
the contrary position ; afterwards the liquid in the first en- 
dosmometer rose 40 other millimetres, and remained sta- 
tionary, and sometimes even fell in the second instrument. 

With the stomach of the cat, alcohol rose 22 millimetres 
in the tube in two hours, when the external surface of the 
membrane was turned towards the interior of the endosmo- 
meter, but with a contrary arrangement it did not rise more 
than 2 millimetres. Sometimes even w^hen, in the first 
position of the membrane, the elevation was from 20 to 24 
millimetres, in the second, there was no elevation. 

With the stomach of the dog, the elevation of alcohol in 
the tube, was 24 millimetres when the mucous surface was 
in contact with water, but was only 16 millimetres when 
placed in the reverse position. Six hours after, the liquid 
rose again 40 other millimetres in the first case, and 25 



LeCT. III. GIZZARD OF THE FOWL. 67 

millimetres only in the second one. In another experiment, 
after the time mentioned, the elevations were 130 millime- 
tres and 6 millimetres. 

With the stomachs which we have hitherto employed, 
endosmose, which is promoted from the internal to the ex- 
ternal surface of the membrane, always takes place from 
water to alcohol, as in Dutrochet's experiments. It is re- 
markable that, with the internal membrane of the gizzard 
of the fowl, endosmose takes place in the contrary way, 
namely, from alcohol to water ; and this holds good, what- 
ever be the position of the membrane with respect to the 
two liquids. This exception, which we at first attributed 
to some defect in the membrane employed, we have re- 
peatedly verified, sometimes by introducing, as usual, the 
alcohol into the interior of the instrument, in which case we 
have seen the alcohol fall below the level, and sometimes 
by placing it externally, when the water constantly mounted 
in the tube. The influence of the position of the membrane 
is equally evident in this case. We shall commence by 
giving the diminutions of height marked in the case where 
the alcohol was in the interior of the instrument. When 
the internal surface of the mucous membrane was towards 
the interior of the endosmometer, the diminution of the height 
of the alcohol was from 24 to 28, and even more than this, 
in the space of six hours, whilst it was only 11 and 12 mil- 
limetres in the other position. In another experiment, 
which we have selected out of a very large number, the 
pure water being placed in the interior of the instrument, 
the elevation was 32 millimetres when the external surface 
of the membrane was towards the interior of the endosmo- 
meter, and 16 millimetres in the other position, in about 
the space of three hours. Consequently endosmose between 
alcohol is promoted from the internal surface to the external 
surface of the gizzard of the fowl. 



68 ENDOSMOSE. LeCT. III. 

Class 3. Bladder of the Ox. — In the last place, we pass 
to the exposition of what we have observed when employ- 
ing for the interposed membrane, the mucous lining of the 
bladder of the ox, in the fresh state, and deprived of the 
muscular layers, as in the case of the stomachs. When 
this membrane was employed, and a solution of sugar intro- 
duced into the interior of the two endosmometers, the height 
which the liquids attained in the tubes was, when the in- 
ternal surface of the membrane was in contact with the 
saccharine liquid, 80, and even 113, millimetres in the 
space of two hours ; but it was only 63, or 72, millimetres 
when the position of the membrane was reversed. The 
current of endosmose, therefore, is promoted in this instance 
from the external to the internal surface of the membrane. 
The contrary effect is obtained with a solution of gum Ara- 
bic. The elevation is 18, and sometimes only 7, milHme- 
tres, when the internal surface is turned towards the interior 
of the instrument containing the gum solution ; whereas, 
when the membrane is arranged the reverse way, the ele- 
vation is 52 millimetres, or, in some cases, 20 millimetres. 

With the solution of gum Arabic, we sometimes saw the 
liquid first fall in both tubes, and after a certain time, rise 
to heights which are pretty nearly the same as those observed 
with a solution of sugar. In one case the liquid fell in both 
instruments 7 millimetres during the first hour ; after that 
time it began to rise again ; and three hours later the ele- 
vation was 12 millimetres in the endosmometer where the 
internal surface of the membrane was in contact with the 
solution of gum, and 8 millimetres in the endosmometer 
where this surface was in contact with the water. With an 
albuminous solution and pure water, endosmose does not 
take place through the mucous membrane of the bladder of 
the ox in a fresh state : the liquid falls in both the tubes, 
whether the interior of the instrument contains the albumin- 



LeCT. III. BLADDER OF THE OX. 69 

ous solution or pure water. Yet it should be mentioned, 
that when the inner surface of the membrane is in contact 
with the albuminous solution placed outside the instrument, 
the diminution of height is less than when the position is 
reversed ; and that the contrary takes place when this solu- 
tion is in contact with the external surface of the mem- 
brane. 

Lastly, with alcohol and pure water there is endosmose 
from the water to the alcohol, as in most cases ; but the 
elevation is sometimes 24 millimetres, sometimes 59 milli- 
metres, when the external surface of the membrane is in 
contact with the alcohol, and sometimes 26, or 37, milli- 
metres in the reverse arrangement. 

Condition of the Membranes. — Some differences, as ob- 
vious as those observed when using fresh membranes, dis- 
appear entirely, or nearly so, when we employ membranes 
dried or altered by a more or less advanced state of putre- 
faction. We have not much varied the experiments proper 
for determining the influence of the condition of desiccation 
and putrid alteration of membranes, and we intend here- 
after to resume our examination of this subject. It is, how- 
ever, certain that when employing the ordinary liquids, and 
interposing between them and pure water the dried bladders 
of a pig and an ox, which have been moistened before the 
experiment, so as to enable them to be applied to the en- 
dosmometer, that there is either no difference in the eleva- 
tion of the liquids in the two tubes, even after several hours 
whatever be the position of the surfaces of the membrane ; 
or a very slight difference in the instrument, in which the 
internal surface of the bladder is towards the interior of the 
endosmometer, sometimes in the other one. When em- 
ploying bladders which have been left for some hours in 
water, we occasionally observe a certain regularity of effects, 
as with fresh bladders ; but if we employ them very wet, 



70 ENDOSMOSE. LeCT. III. 

after they have soaked a whole night in water, we observe 
no elevation in the liquids of the endosmometers, or the 
elevation, which is always slight, is equal in the two tubes. 
We can, in some cases, explain the anomalies presented by 
the bladders in this state. Thus any one can perceive on 
a wet bladder, that the muscular fibres are swollen, in pro- 
portion to the time the bladder has been in water. These 
muscular fasciculi acquire thus a certain thickness, they 
approximate to one another, and acquire, in some degree, 
a condition analogous to that of freshness. But w^e have 
several times seen that endosmose does not take place with 
bladders, gizzards, and fresh stomachs, from which the 
muscular laminse had not been removed. If the bladder be 
slightly moistened, the muscular bundles are, it is true, a 
little more expanded, but nevertheless there exist between 
them interstices through which endosmose certainly takes 
place : the inequality of the interstices, however, even in 
two symmetrical portions of the same bladder, must produce 
vague and uncertain results. 

We have only employed the gizzard of the fowl in a more 
or less altered state, in order to determine what influence 
putrefaction has over the phenomenon of endosmose ; a 
great uncertainty exists with respect to the results furnished 
by the gizzard in this state. Sometimes, indeed, the liquid 
did not pass at all, sometimes it had an equal elevation in 
both instruments. Whatever were the liquids employed, or 
the position of the membrane, endosmose was energetic, 
but sometimes in one direction, and sometimes in the other; 
and occasionally, indeed, it was depressed to the level of 
the liquids in both instruments. In speaking elsewhere of 
that which we observed in making use of the skin and gas- 
tric mucous membrane of certain animals, we have remarked 
that the phenomena of endosmose vary according as we em- 
ploy these membranes immediately after death, or some hours 



LeCT. III. CONCLUSIONS. 71 

subsequently. All these facts demonstrate clearly the inti- 
mate relation which exists between the phenomenon of en- 
dosmose and the physiological condition of the membranes. 

The phenomenon of endosmose, like every thing going 
on in organized tissues, is devoid of that constancy and re- 
gularity observed in physical phenomena elsewhere. To 
this variable and accidental organic condition of the fresh 
membranes must be ascribed the singular fact, that while 
in certain cases we obtain an elevation of perhaps 80 milli- 
metres, yet sometimes with the same liquid, the same mem- 
brane, and in the same relative position, the rise does not 
exceed 10 millimetres. We must also ascribe to a constant 
anatomico-physiological condition, connected with the func- 
tion of the same membrane, that constant difference of ele- 
vation in the two different positions of the membrane, what- 
ever this difference may in other respects be. It is important 
to study the phenomenon with the view of recognising the 
accidental circumstances which cause the variation of en- 
dosmose through the fresh membranes ; as, for example, 
the privation of nourishment in relation to the stomach, the 
administration of certain substances to the animal before 
killing it, &c. With this object we made one comparative 
experiment only, which induces us to believe that endos- 
mose through the skin of the eel is most energetic when 
the skin has been removed after the animal has been for 
some time out of the water. 

Conclusions. — The novelty and importance of the results 
we have obtained, must be my excuse for relating them in 
this extended form. The general conclusions which we 
have deduced from them are as follows : — 

1st. The membrane interposed between the two liquids 
is very actively concerned, according to its nature, in the 
intensity and direction of the endosmotic current. 

2dly. There is, in general, for each membrane a certain 



72 " ENDOSMOSE. LeCT. III. 

position in which endosmose is most intense ; and the cases 
are very rare in which, with fresh membrane, endosmose 
takes place equally, whatever be the relative position of the 
membrane to the two liquids. 

3dly. The direction which is most favourable to endos- 
mose through the skins, is usually from the internal to the 
external surface, with the exception of the skin of the frog, 
in which endosmose, in the single case of water and alcohol, 
is promoted from the external to the internal surface. 

4thly. The direction favourable to endosmose through 
stomachs and urinary bladder varies, with different liquids, 
much more than that through skins. 

5thly. The phenomenon of endosmose is intimately con- 
nected with the physiological condition of the membranes. 

6thly. With membranes, dried or altered by putrefaction, 
either we do not observe the usual difference arising from 
the position of their surfaces, or endosmose no longer takes 
place. 

Exosmose. — To give an accurate account of the subject 
of our experiments, and of the conclusions we have drawn 
from them, it is necessary to consider exosmose in a point of 
view different from that in which it has hitherto been re- 
garded. The augmentation of volume presented by the 
internal liquid, which is usually the denser one, is consi- 
dered by Dutrochet as the result of a difference between 
the in-going strong current and the out-going weak current. 
According to this view, that liquid which receives from the 
other one more than it gives, should increase in proportion 
to the excess which it receives, or to the difference between 
the strong current and the weak one. But all the facts 
which we have observed, lead us to the conclusion that 
different membranes allow the passage of water to the liquid 
in the endosmometers more easily in one direction than in 
another, and more readily with some liquids than with 



LeCT. III. EXOSMOSE. 73 

others. But a great number of difficulties are met with in 
considering the phenomena in this manner. We refrain 
from enumerating them, as they must present themselves to 
any one who has followed us in the exposition of the facts 
we have observed. We shall merely observe that, in 
ascribing every thing to endosmose, the presence of the 
solution of gum, or of sugar, in the interior of the endos- 
mometer, gives us no explanation of the phenomena w^hich 
are observed with the internal membrane of the stomach of 
the lamb, and with the mucous membrane of the bladder of 
the ox; and that these phenomena are susceptible of a more 
easy and natural explanation, by assuming that, by exosmose, 
the various membranes give to the different liquids a more 
or less easy passage towards the water, according to the 
surface with which these liquids are in contact ; and by 
supposing that the passage of the water towards the denser 
liquid is always constant, in accordance with the almost gene- 
ral law of endosmose. But it was necessary to have recourse 
to experiment to determine whether our mode of consider- 
ing the phenomenon was correct ; and it was requisite not 
only to prove the existence of exosmose, as M. Dutrochet 
had done, but also to measure it in the same manner as 
endosmose. 

In these researches we preferred using the skins of frogs 
and eels, and employing saltwater as the denser liquid, and 
also, in some cases, a solution of sugar. 

We began by preparing two endosmometers in the usual 
way ; in one, putting the skin of the frog or eel with its 
internal surface towards the interior of the instrument ; and, 
in the other, placing the membrane in the contrary posi- 
tion. We introduced into the two endosmometers equal 
volumes of salt water of known density, and plunged these 
instruments into two separate glass vessels, each contain- 
ing a volume of distilled water equal to that of the salt 



74 ENDOSMOSE. LeCT. III. 

water. After some hours, we carefully measured the vo- 
lumes of liquid contained in the endosmometers, and 
also those of the distilled w^ater remaining in the two ves- 
sels, and thus we found which of the two liquids had risen 
most in the tubes. We observed that endosmose from 
water to a saline solution through these skins, was most 
promoted from the internal to the external surface. By 
determining the density of the liquids contained in the 
two vessels, we found that in the endosmometer in which 
the volume of salt water was most increased, the density of 
the liquid was preserved better than in the other ; and, vice 
versa, in the vessel in which the diminution of distilled water 
was greatest, the quantity of the saline solution introduced by 
exosmose was less than in the other vessel from which a 
smaller volume of distilled water had disappeared. 

In the following table are given the numbers furnished 
by two of the numerous experiments which we made, and 
which led us to these results. The first column indicates, 
in tenths of cubic centimetres, the volumes of the liquids 
in the endosmometers after the experiment ; the second 
column, the weight of a given quantity of these liquids ; 
the third, the volumes of distilled water found in the two 
external vessels after the experiment ; and the fourth, the 
weight acquired during the experiment by a given quantity 
of water in these same vessels. The weight of the same quan- 
tity of the saline solution, before the experiment, was 17-350 
grammes ; and that of an equal quantity of distilled water 
16-025 grammes. 



LeCT. III. EXOSMOSE. 75 

Experiments with Water and a Solution of Common Salt. 



I. 


II. 


III. 


IV. 


Volume of the Li- 


Weight of a given 


Volumes of distilled 


Increase of Weight, 


quids in the En- 


Volume of the 


Water in the out- 


during the Ex- 


dosmometers af- 


Liquids. 


er Vessels after 


periment, of a 


ter the Experi- 




the Experiment, 


given Volume of 


ment, in cubic 




in cubic centi- 


Water in the 


centimetres. 




metres. 


outer Vessels. 


Skin of the Frog. 








150 c. c. 


17-835 gr. 


112-5 c.c. 


16-105 gr. 


149 


17-680 


113-5 


16-405 


Skin of the Eel. 








222-5 c. c. 


17-145 gr. 


200C.C. 


16-170 gr. 


217-5 


47-130 


. 205 


16-220 



In some cases, we precipitated the chlorine of the salt 
contained in the two external vessels, by means of nitrate 
of silver. The last column of this second table gives the 
quantity of chloride of silver thus obtained. 

Experiments with Water and a Solution of Common Salt. 



I. 

Volumes of the Li- 
quids in the En- 
dosmometers af- 
ter the Experi- 
ment. 



II. 

Weights of a given 
Volume of the Li- 
quids. 



III. 

Volumes of distilled 
Water in Outer 
Vessels after the 
Expeiiment. 



IV. 

Chloride of Silver 
obtained from the 
Salt found in the 
outer Vessels. 



Skin of the Frog. 
172 c. c. 
171 



17-190 gr. 
17-175 



16a c. c. 
161 



190 gr. 
280 



We have observed a similar result with a solution of 
sugar and the skin of the eel ; the weight of a given vo- 
lume of the saccharine solution was, before the experi- 
ment, 18-180 gr. 



^76 ENDOSMOSE LeCT. III. 

Experiments with Water and a Solution of Sugar. 



I. 

Volumes of the Li- 
quids in the En- 
dosmometers af- 
ter the Experi- 
ment. 



II. 

Weights of a given 
Volume of the Li- 
quids. 



III. 

Volumes ofdistiiled 
Water in the Out- 
er Vessels after 
the Experiment. 



IV. 

Increase of Weight, 
during the Expe- 
riment, of a given 
Volume of Wa- 
ter in the Outer 
Vessels. 



Skin of the Eel. 
193 c. c. 
191 



1 8-035 gr. 
18010 



181 c. c. 
lo3 



16-045 gr. 
16-050 



These fact^ cannot be explained by assuming that the 
elevation and increase of volume of the liquid of the two 
endosmometers arise micrely from the difference between 
the current of endosmose and that of exosmose. If it 
were so, the endosmometer in which the largest quantity 
of saline solution had accumulated, ought to contain a 
liquid less dense than that in the other which presented 
a less augmentation of volume. These facts may be, on 
the contrary, completely explained, by assuming that the 
current of endosmose has been equal, or nearly so in the 
two positions of the membrane, and that the difference 
depends altogether in the current of exosmose, which is 
weakest in that endosmometer in which the elevation is 
most considerable, and stronger in the one in which the 
elevation is the slightest. These results give a great im- 
portance to the influence of the membrane interposed be- 
tween the two liquids in the phenomenon of endosmose ; 
for, by its particular nature alone and its physiological 
function, we can explain the more or less easy passage of 
different denser liquids towards other less dense ones 
through the membrane itself. 

Endosmose applied to Physiology. — We certainly feel the 
necessity of having recourse to other experiments in order 



LeCT. III. APPLIED TO PHYSIOLOGY. "Ill 

to exhaust the subject of endosmose, which must play so 
important a part in all the acts of organized beings. It is 
certain that the results which we have obtained in this 
series of experiments, and the view we have taken of en- 
dosmose, lead to a more correct appHcation of the phe- 
nomenon of endosmose to the functions of organized beings. 
Endosmose promotes the Mucous Secretion of the Skin. — 
The exosmose of a solution of sugar, of albumen, and of 
gum, towards w^ater, is promoted from the internal to the 
external surface, in all the skins examined. It is precisely 
in this same direction through the skin of the torpedo, the 
eel, the frog, and other animals, that a copious secretion of 
mucus takes place. The endosmose of water to a solution 
of sugar, of gum, and of albumen, is less intense from the 
external to the internal surface of the skin than when it 
takes place by the reverse arrangement. Consequently, if 
we do not admit that this secretion of mucus, and this weak 
absorption of the -water wherein these animals live (func- 
tions which, for their normal performance, ought always to 
bear a certain relation to each other,) are entirely due to the 
phenomena we have discovered ; at all events, we cannot 
deny that they must be promoted by it. Undoubtedly this 
function of the skin would not go on, or would do so im- 
perfectly, if in these animals which live constantly in water 
this membrane acted endosmotically in an opposite direction 
to that which we have found it to do. 

Endosmose in relation to the Function of the Stomach. — 
This constancy observed in the direction most favourable 
for endosmose and exosmose through skins, does not hold 
good for the mucous membrane of the stomach of different 
animals. But every one knows how much more compli- 
cated the function of the stomach is, and that all the sub- 
stances introduced into this organ are either not absorbed, or 
are absorbed unequally. Moreover, we repeat, that this 



78 ENDOSMOSE LeCT. III. 

subject requires elucidation by fresh experiments. When 
we remark that the direction most favourable to endosmose 
between water and a saccharine solution, for example, is 
not the same for the stomach of a ruminant as for the stomach 
of a carnivorous animal ; it clearly follows that the phe- 
nomenon of endosmose must be intimately connected with 
the great differences which exist in the digestive functions 
of these two orders of animals. I am anxious to explain 
to you all the details of the experiments which I made with 
Professor Cima on the subject of endosmose, being well 
convinced of the great importance of this phenomenon in 
the vital functions. 

Ovules nourished and Spermatophora opened by Endos- 
mose. — It is by endosmose that physiologists now explain 
the manner in which the nutrition of the ovules in the ovi- 
ducts of mammalia is effected ; and how the sacs, which 
contain the sperm of the cephalopodus molluscs (or the 
spermatophora) open immediately they are brought in con- 
tact with water. 

Endosmose of Cells. — A cell is the elementary organ of 
all animal and vegetable tissues, and cell-life involves an 
act of endosmose : this show^s how much the phenomenon 
of endosmose requires to be more completely studied, in 
order that we may be enabled to make of it all the appli- 
cations of which it is susceptible. 

Endosmotic Action of Purgatives. — I cannot conclude 
this lecture without referring to the recent experiments of 
Poiseuille, made with the view of explaining by endosmose 
the purgative action of certain substances. He found that 
there was endosmose through animal tissues from the serum 
of the blood to Seidlitz water, and to solutions of sulphate 
of soda and common salt. Now this is precisely what hap- 
pens when we use these medicines internally: the rejected 
excrements contain an abundant quantity of albumen. In 



LeCT. III. OF LIQUIDS IN MOTION. 79 

this case we must admit that endosmose takes place through 
the capillary vessels of the intestine, from the serum of the 
blood to the saline solution introduced into the alimentary 
canal. 

Endosmose of Liquids in Motion. — But to remove all doubt 
of the propriety of Poiseuille's applications of this fact, it 
was necessary to demonstrate that endosmose takes place 
when one of the liquids is in motion, and is being con- 
tinually renewed. This has been recently done by Dr. 
Bacchetti, who has shown that the rapidity of endosmose is 
considerably augmented when one of the liquids was con- 
tinually renewed. This result, moreover, is in accordance 
with the principles of the theory of endosmose : the inter- 
change of liquids, constantly going on through the mem- 
brane, leads to the suspension of the action of endosmose ; 
or, in other words, the conditions for the production of the 
phenomenon are so much the better preserved, as the liquids 
remain longer without mixing. Poiseuille has also shown 
that endosmose ceases to take place in a membrane after a 
certain time of action, but that the membrane re-acquires 
this property by submitting it to the action of other liquids. 

Remarkable Influence of Morphia. — The most remarkable 
fact discovered by Poiseuille is, that of the influence ex- 
ercised by hydrochlorate of morphia. This substance, 
when added to saline solution, very considerably weakens 
the endosmose from the serum to the solution ; and ulti- 
mately changes the direction of the current. This fact has 
been confirmed by Dr. Bacchetti. How can we make an 
entire abstraction of this fact in the explanation of the action 
of morphia, and of the preparations of opium in diarrhoea, 
as W'Cll as of the constipation which they produce ? 



80 ABSORPTION AND EXHALATION. LeCT. IV. 



LECTURE IV. 

ABSORPTION AND EXHALATION IN ANIMALS AND PLANTS. 

Argument. — Absorption in animals consists of two acts, imbibition and 

transmission. All vessels absorb ; proofs that blood vessels absorb ; 

proofs that the lymphatics and lacteals absorb. Physical conditions of 

absorption. Laws of absorption. 
Exhalation; its mechanism similar to that of absorption. Transformations 

effected during absorption and exhalation. 
Absorption in plants; summary of facts concerning if. The movement of 

the juices of plants inexplicable by capillarity and imbibition merely. 

Sponglets. Evaporation or transpiration by the leaves. The ascent of 

liquid in plants depends on both the root and leaves. 

The preceding lectures on the phenomena of capillarity, 
imbibition, and endosmose, have been delivered principally 
for the purpose of preparing you for the study of absorption 
and exhalation. It is not for me to speak of the researches 
that have been made expressly for the purpose of determin- 
ing on which of the various organs these functions especially 
devolve. In treatises on physiology, you will find them 
exclusively ascribed sometimes to the veins, sometimes to 
the lymphatic vessels. 

We find it difficult to account for so many discussions 
when we reflect on the structure of all these different tissues, 
and on the necessary existence of the phenomena of absorp- 
tion and exhalation in a large series of the lower animals 
apparently devoid of lymphatic vessels. 

Absorption in Animals consists of Imbibition and Trans- 
mission.' — Absorption, considered as a function of living 



LeCT. IV. IMBIBITION AND TRANSMISSION. 81 

animals, consists not merely of the imbibition of a liquid by 
a tissue, but also of the passage into the blood-vessels of 
the liquid with which such tissue is in contact. It is at the 
blood that the absorbed matter ought to arrive ; this is the 
final object of the phenomenon. Let us distinguish, then, 
two things in absorption : the introduction of the substance 
to be absorbed through the interstices of an organized body, 
and its subsequent passage into the circulation. 

It is easy to demonstrate the existence of the first part of 
this function. Here is a frog, whose inferior extremities 
only, have been immersed for several hours in a solution of 
ferrocyanide of potassium. If we remove the animal from 
the liquid, carefully wash it wdth distilled water, and then 
cut it in pieces, we can easily prove that the solution has 
penetrated into every part. Wherever we touch the viscera 
or tissues with a glass rod moistened with a solution of the 
chloride of iron, a more or less deep> blue stain is pro- 
duced. 

I shall the more insist on this manner of demonstrating 
the reality of absorption, because it explains to us very 
clearly the two parts of which we have stated this function 
to consist. If a living frog be immersed, by its inferior ex- 
tremities only, in a solution of ferrocyanide of potassium, 
and the animal sooa after killed, we can scarcely detect 
any traces of the salt in the muscles of the legs and thighs ; 
whereas the heart and lungs give very distinct evidence of 
it when they are touched with chloride of iron. 

One experiment more, and the conclusion will be evi- 
dent. I immerse another frog, which has been dead for 
some minutes, in th« same solution, and leave it there for 
the same time that I did the other. When tested, the lungs 
and heart offer no greater evidences of the presence of the 
ferrocyanide than does any other part of the body. 

Here is the explaiiation of these experiments : — The solu- 
6 



82 ABSORPTION AND EXHALATION. LeCT. IV. 

tion was introduced into the body of the frog simply by 
imbibition ; and this phenomenon, being effected in the 
living as well as in the dead frog, certainly cannot be re- 
garded as different from the imbibition which we have 
already studied, which belongs to both organic and in- 
organic bodies, and which is the consequence of their 
cellular and vascular structure, &c. 

But there is something more than this. In the heart and 
lungs of a living frog we find a much larger quantity of the 
absorbed solution than in the other parts of the body, 
although these latter were much nearer the part immersed. 
These viscera are the centre of the circulatory system : in 
them commence or terminate the trunks of the blood-vessels. 
The solution of the ferrocyanide, therefore, has penetrated 
the blood-vessels by imbibition, mingled with the blood, 
and thus arrived at the heart and lungs. 

We have another very simple experiment proving the 
same facts : — I take two frogs, and from one remove the 
heart ; the animals are equally lively. Both are placed in a 
large glass containing a solution of the extract of nux vomica. 
The animal with the heart is soon poisoned, and long before 
the other becomes affected. 

All Vessels absorb. — It has for some time been a subject 
of discussion whether the lymphatic vessels or the veins 
were exclusively endowed with the power of absorption : 
that is, whether a substance could be directly introduced 
into the blood-vessels by passing through the tissue of their 
sides ; or whether it must necessarily first pass through the 
lymphatics. As every part of an organized being more or 
less easily imbibes water, saline solutions and serum, it is 
clear that the first part of absorption may take place through 
the sides of the lymphatics, as well also as through those of 
the blood-vessels. Microscopic anatomy, by unveiling the 
manner in which the blood-vessels and lymphatics terminate, 



LecT. IV. ABSORPTION BY BLOOD-VESSELS. 83 

has confirmed the preceding conclusion. I feel bound to 
cite here the principal results of the observations of our 
countryman Panizza. 

There is no fact which demonstrates the existence of free 
extremities in the ramifications of blood-vessels, which 
every where present a very close and continuous reticulated 
texture. The arterial network is uninterruptedly continuous 
with the venous network which, in general, predominates 
over the former. The lymphatic system, likewise, never 
terminates by independent extremities, but every where 
presents the aspect of a very fine and close trellis work. 
Anatomy, which agrees with physiology, leads us to the 
conclusion that the first part of absorption can be effected 
only by the aid of the porosities proper to the structure of 
organized beings. In this way the absorbed matters arrive 
at, and mix with, the blood, the chyle, and the lymph, and 
are carried away by these liquids, and distributed over the 
body. 

Absorption by Blood" Vessels. — I consider it now almost 
superfluous to quote the experiments of Magendie, Segalas, 
and the later ones of Panizza, all of which prove that ab- 
sorption takes place principally by the intervention of the 
blood-vessels. 

The following is the manner in which the last mentioned 
physiologist proceeded : — Having made an incision ten 
inches long in the belly of a horse extended on the ground/ 
he drew out a fold of small intestine, in which arose several 
small veins, which, after a short course, terminated in a 
single very large mesenteric trunk, before any small veins 
from the glands had emptied themselves into it. This fold, 
nine inches in length, was tied by a double ligature in such 
a manner that it could receive blood by a single artery only, 
and could return none to the heart except through the ve- 
nous trunk above described. An aperture was then made 



84 ABSORPTION AND EXHALATION LeCT. IV. 

into the fold for the purpose of admitting a brass tube, 
which was so fastened by means of thread that the substance 
to be introduced should not touch the bleeding edge of the 
opening. This being done, a ligature was passed under the 
vein receiving the blood from the fold. The ligature was 
tightened ; and, in order that the circulation should not be 
stopped, the vein was opened to allow the escape of the re- 
turning blood. Then, by means of a glass funnel and the 
brass tube, some conc€ntrated hydrocyanic acid was intro- 
duced into the fold, and the tube then closed. The venous 
blood returning from the intestine was immediately collected, 
and found to contain hydrocyanic acid ; but the animal pre- 
sented no symptoms of poisoning, notwithstanding that the 
nerves and lymphatics remained untouched. 

In another experiment Pannizza, instead of tying and 
opening the venous trunk where the small veins discharged 
themselves, merely compressed it at the moment the hydro- 
cyanic acid was introduced. There was no symptoms of 
pois-oning ; but shortly after the removal of the pressure, 
symptoms of poisoning appeared ; and,^ the vein being 
opened, the contained blood was found to be impregnated 
with the acid. 

Lastly, in a third experiment, Panizza quickly, but care-^ 
fully, removed, all the lymphatic vessels and nerves of the 
intestinal fold; and,, hydrocyanic acid being poured in, 
speedily destroyed the animal, provided that the vein was^ 
untouched. Venous absorption is thus proved by the most 
accurate experiments. 

In some works on physiology it is stated that the fact of 
substances being detected in the urine, a few minutes after 
their introduction into the stomach, is opposed to the opinion, 
that absorption takes place by means of the blood-vessels. 
But this objection soon falls to the ground, when we con- 
sider the rapidity of the circulation of the blood. 



LecT. IV. BY LYMPHATICS AND LACTEALS. 85 

Absorption hy Lymphatics and Lacteals. — On the other 
hand, that absorption can be also effected by the lymphatic 
vessels, is a fact too well known and too evident, to render 
a demonstration of it necessary. Kill an animal two or 
three hours after it has taken food, expose the intestines, 
and carefully examine the mesentery, and you will find that 
the chyliferous vessels are filled with a milky liquid analo- 
gous to that which flows abundantly from the thoracic duct, 
which is the principal reservoir into which these vessels dis- 
charge their contents. This liquid is the chyle which, by 
the act of digestion, is formed in the intestine, from which 
it is absorbed by the chyliferous vessels. How many ex- 
amples has pathological anatomy furnished us with, in 
which these vessels have been found full of pus, by reason 
of their proximity to suppurating parts ! The chyliferous 
and lymphatic vessels are, therefore, endowed with the 
power of absorption. 

Physical Condition of Absorption.^-In a w^ord, absorption 
is always effected under the following conditions :^- 

1st. A vessel with organic sides or walls. 

2dly. An anterior liquid capable of being imbibed by the 
tissue composing the walls. 

3dly. An internal liquid, also capable of being imbibe4 
by the walls ; of intermixing with the exterior liquid ; and 
of circulating in the vessel with more or less rapidity. 

Nothing, consequently, can be more physical than a 
phenomenon thus constituted. 

I will demonstrate, by an experiment, the truth of this 
assertion. Here is a long piece of vein taken from a large 
animal ; it is attached at one end to a tube connected with 
an opening in the lower part of the side of a glass bottle ; 
the other extremity is tied to a small bent glass tube, fur- 
nished with a stop cock. I fill the bottle, and, consequently, 



86 ABSORPTION AND EXHALATION. LeCT. IV. 

the vein also, with water. I immerse a portion of the vein 
in water, acidulated with sulphuric or hydrochloric acid. 

Fig. 5. 




Apparatus to illustrate Physical Absorption. 

At first the liquid in the bottle gives no indications of the 
presence of the acid ; but after a certain time it does. If, 
instead of waiting some time, and leaving the liquid in re- 
pose, I open the stop cock, I can immediately detect the 
presence of the acid in the liquid which flows out ; but in 
the bottle it is not yet discoverable. That which happens 
with a portion of vein, will take place in the same way with 
the arterial trunk, and with tubes of clay, pasteboard and 
wood. If the acidulated solution be contained in the in- 
terior of the vein ; and if into the liquid of the basin, in 
which the vein is immersed, we pour some tincture of lit- 
mus, the same phenomenon is observed ; that is, the acid 
will pass out through the coats of the vein, with a facility 
proportionate to the velocity of the current. The conditions 
of the phenomenon are always the same : two liquids 
miscible with each other, and separated by a membrane 
capable of imbibing them, and the movement of the inter- 



LeCT. IV. LAWS OF ABSORPTION. 87 

nal liquid which carries, in a given direction, the liquid 
"which has transversed the membrane.* 

Suppose for a moment that the direction of the circulation 
of the blood was inverse to that which it really is, but with- 
out any alteration in the structure and disposition of the 
blood-vessels : we should then no longer say that the veins 
absorbed, but, on the contrary, that absorption took place 
by the arteries. Such is the very simple physical phenome- 
non of this function. 

Laws of Ahsorption.—l am anxious also to demonstrate 
to you the laws of absorption, which were discovered by 
experimental physiology ; and you will then readily perceive, 
that they are the necessary consequences of the principles 
which we have laid down. 

1st. " The more the matters are soluble, divided and 
fitted for entering into combination with the organic juices, 
and for becoming constituent parts of the blood, the more 
easily are they absorbed." 

The language used in stating this law is not very scientific, 
but I wish to give it to you as it is found in the most modern 
accredited works on physiology. This law is an evident 
consequence of the manner in which we have explained the 
phenomenon of absorption. It is desirable that physiolo- 
gists should study with attention the various degrees of 
power with which different liquids are imbibed by organic 
tissues, for such study will certainly prove highly important 
to therapeutics. 

Let me show you some facts which will assist us in 
understanding these researches. We have here two rabbits ; 

* This apparatus I have long been in the habit of using in the lecture 
room, (see my Elements of Materia Medica^xol. i. p. 112, 2d edit., 1842.) 
It is more convenient in practice to have the vein connected with the 
bottle by a stopcock, as represented in the above figure, which differs in 
this respect from the figure given in Matteucci's lectures.— J. P. 



88 ABSORPTION AND EXHALATION. LeCT. IV. 

about two hours ago some water was introduced into the 
stomach of the one, and some oil into that of the other. 
In the stomach of the first there remains not a trace of the 
water, but in that of the second we find all the oil; and it 
•would still have been found there had we delayed opening 
the animal for several hours longer. If, instead of pure 
water, we had used a mixture of water and alcohol, the 
absorption would have been more rapid. An acid or saline 
solution would also have been absorbed, but not so rapidly 
as pure water. 

" 2d. The intensity of the absorbing power of different 
organs is chiefly dependent on the number of their vessels, 
the flaccidity of their tissue, and the conducting power of 
the parts which cover them." 

I am repeating word for word what I find in works on 
physiology. It is evident that the terms flaccidity of tissue, 
and the conducting power of the parts which cover them, 
mean nothing more than that the texture of organic solids 
is more or less favourable to imbibition. The greatest 
number of vessels merely signifies the largest number of 
points of contact between the body to be absorbed, and the 
liquids with which it is to be mixed and carried away. 
This is the reason why the lungs, as we have seen, are the 
best fitted for absorption, and why they are the first to 
manifest the presence of the absorbed body. In fact, ana- 
tomy teaches us that the lungs, more than any other part of 
the animal economy, possess a structure fitted for imbibition, 
and a highly developed vascular system. The cellular tissue, 
likewise, is very permeable to liquids, but not being so well 
supplied with blood-vessels as the lungs are, absorption is 
there effected more slowly. The skin, on the contrary, 
being covered by epidermis, which is of a very compact 
texture, and devoid of blood-vessels, performs with diffi- 



LeCT. IV. LAWS OF ABSORPTION. 89 

culty this function ; but, by removing the epidermis, we 
render the skin more capable of absorption. 

" 3dly. Absorption varies according to the quantity of 
liquid which exists in the organism, and is in the inverse 
ratio of the plethoric state of the animal." 

•If you remember the phenomenon of imbibition, you will 
easily comprehend this law of the function. A mass of 
sand, if saturated with liquid, Cannot further imbibe ; and, 
on the other hand, imbibes so much the more rapidly, as it 
is further removed from the point of saturation. 

Dutrochet exposed a plant to the air until it had lost by 
evaporation 0.15 of its weight; and afterwards, by plunging 
it into water, he found that in each of the first four hours 
of immersion, it absorbed ls^05 (20 grains,) and lost 0«^40 
(8 grains ;) subsequently it absorbed only 0^^45 (9 grains,) 
and lost as much by exhalation. Edwards found that frogs 
absorbed water the more rapidly in proportion as they had 
lost more of their weight by transpiration. 

Magendie mentions that a dog, from which a large quan- 
tity of blood had been drawn, died rapidly from poisoning 
by strychnia; whilst another animal, into whose veins a 
large quantity of water had been injected, did not present 
symptoms of poisoning. 

" 4thly. Within certain limits, absorption is in proportion 
to the temperature of the absorbing body, and of the body 
absorbed." 

Every one knows that warm drinks operate more quickly 
than cold ones. So also with imbibition, which, as we have 
seen, varies greatly according to the temperature. I have 
said, that this variation can only be effected within certain 
limits, for beyond these the structure of the organized body 
will be altered. 

" 5thly. According to Fodera, the electric current favours 
absorption." 



90 EXHALATION. LeCT IV. 

If we admit the experiments of this physiologist, it is not 
easy to explain the fact now stated, because, when we em- 
ploy the electric current in imbibition, we do not observe 
this influence. The fact mentioned by Porret alone,* and 
which consists in the transit of water from the positive to 
the negative pole, may in some way explain the results ob- 
tained by Fodera. 

" 6thly. Lastly, absorption varies according to the ra- 
pidity with which the liquid moves in the absorbing ves- 
sel." 

It is unnecessary to state how this rapidity serves to 
carry more or less quickly, and to a given distance, the 
absorbed body. It is equally easy to understand, that as 
the molecules of the liquid contained in the vessel are the 
more frequently renewed, so the actions of affinity, which 
tend to promote the absorption of the body into the inte- 
rior of the vessel, become more energetic. This, proba- 
bly, is the reason why absorption is slower by the chylife- 
rous and lymphatic vessels than by the veins. Hence, 
many coloured substances, alcoholic liquids, and saline 
solutions, introduced into the stomach, are found in the 
blood, without our being able to discover them in the chy- 
liferous vessels and the thoracic duct. Friction on the skin, 
and the peristaltic motion of the bowels, in this way aid 
absorption by promoting the movement of the liquids in 
the vessels. 

Exhalation. — The function of exhalation is, in general, 
effected by the same mechanism, and under the same laws 
as those of absorption. Through the coats of a vessel, 
capable of imbibing the contained liquid, a portion of it is 

* The fact is alluded to by Dr. Faraday {Experimental Researches in 
Electricity^ 13th series, § 1646.,) and has been made the subject of a paper 
by Mr. James Napier (O/i Electrical Endosmose ; in the Memoirs and 
Proceedings of the Chemical Society, vol. iii. p. 28.) — J. P. 



LeCT. IV. TRANFORMATIONS EFFECTED. 91 

constantly passing out, or exhaling. The portion which 
escapes varies according to the nature of the liquid ; that 
is to say, according to the greater or less facility with 
which it is imbibed by the tissue of the vessel. In pro- 
portion as the sides of this vessel are externally more or 
less moist, so will the internal liquid flow out with more or 
less difficulty. The exhalation will be augmented if, in 
consequence of the very large quantity of contained liquid, 
the walls of the vessel are subjected to increased pressure. 
All these particularities of exhalation, which result from 
what we regarded simply as a physical phenomenon, and 
which depend on the same principles as absorption, are de- 
monstrated by experimental physiology. 

Edwards has proved, that cutaneous exhalations is, in 
some cases, ten times greater in dry than in moist air, and 
that it is doubled in passing from 0° to + 20° centig. 
[= 32° Fahr. to 68°.] He also found that transpiration was 
augmented by agitating the atmospheric air around the 
body of the animal. These results are evidently the very 
natural consequences of physical principles, too well known 
to be repeated here. 

Transformations effected by Jib sorption and Exhalation. — 
Some of the phenomena of absorption and exhalation in^ 
living beings, are accomplished by the transformation of 
the absorbed or exhaled body. The liquid which is imbibed 
by a membrane, and exhaled from its opposite surface, is 
not identical with that which was placed in contact with 
the absorbing membrane. This happens in most of the 
cases of exhalation, and principally in the secretions. 

We are very far from expecting to find, in the present 
condition of physico-chemical knowledge, an explanation 
of the phenomena of the secretions. We must admit that 
they form as yet one of the most obscure subjects of the 
animal economy. With respect to exhalation it may be 



92 ABSOllPTlON AND EXHALATION. LeCT. IV. 

observed, that in some cases it is effected by a kind of fil- 
tration. A liquid which contains in suspension insoluble 
particles, is separated by filtration into two portions : the 
liquid part, which is imbibed by the substance of the 
filter, and is strained ; and the solid part, which remains on 
the filter. Anatomists know that by injecting into the veins 
or arteries a solution of gelatine coloured by very finely 
powdered vermilion, the solution becomes colourless when 
it percolates through the coats of the vessels. Every con- 
tusion of the skin produces a spot, the centre of which is 
of a dark blue, and the circumference of a green colour 
surrounded by yellow. In this case, the extravasated clot 
of blood is separated from the serum, which is imbibed by 
the neighbouring tissues. 

Do not forget the fact which has been demonstrated to 
you respecting imbibition. Salt w^ater becomes fresh by 
traversing a bed of sand ; while a solution of carbonate of 
soda, filtered under the same conditions, becomes denser. 
Imbibition, capillarity, and the simple play of molecular 
attraction, can overcome affinities. The old notion, there- 
fore, according to which the secreting organs were consi- 
dered as mere .filtering apparatus, is not entirely without 
foundation. 

In another lecture we shall find, that membranes, and in 
general all organized tissue, are capable of being traversed 
by gaseous bodies. Fodera was the first to prove, that 
sulphuretted hydrogen, enclosed in a portion of the intes- 
tinal tube, diffuses itself throughout the body of the animal 
and occasions death. 

Absorption in Vegetables. — A few words, also, on absorp- 
tion in plants. Here, in these small glasses, are a great 
number of plants, more or less immersed in a very dilute 
solution of acetate of iron. Some of them are haricots 
[kidney -beans, Phaseolus vulgaris;] others beans [Vicia 



LeCT. IV. ABSORPTION IN VEGETABLES. 93 

Faba.] Some have been deprived of their leaves ; others 
have been cut in two, and immersed by their stalks only : 
these have been deprived of the extremity of the roots; 
those have been put into the liquid after the roots had 
withered. Lastly, others were completely dried before 
they were placed in the fluid. 

By employing ferrocyanide of potassium as a test, we can 
demonstrate the ascent of the ferruginous solution in the 
interior of each of the plants, above the level of the liquid 
in which they are immersed. 

We perceive, that in the living plant, furnished with, 
leaves and roots, the liquid has been considerably ele- 
vated ; in those that were withered, and which have re- 
covered their freshness in the aqueous solution, absorption 
has been yet greater; while, lastly, it is most abundant 
in those which had been previously deprived of their roats. 
Whatever may be the liquid em.ployed, it is always ab- 
sorbed by the plant, except in the case of some acid alka- 
line, or very concentrated saline solution, which by altering 
and destroying the structure of the plant, and by coagulating 
its juices, cannot be absorbed by it. 

Our best information on this subject is d'erived from 
Saussure's celebrated work,, entitled, Recherches Ckimiques , 
sur la Vegetation. Here is a summary of it : — 

1st. The roots absorb aqueous solutions of salts, but in 
a much smaller proportion than water. 

2dly. Removal or alteration of the roots, and, in general, 
every thing which lessens the force of vegetation, favours 
the introduction of salts into the plant. 

3dly. A plant does not equally absorb all the salts con- 
tained in the same solution. This is confirmed by the 
fact, that certain salts are invariably met with in some 
plants. Professor Piria has always found manganese in 
the seeds of Lupinus albus. 



94 



ABSORPTION AND EXHALATION. 



Lect. IV. 



Fig. 6. 



Let us now examine whether the absorption of the nutri- 
tive juices, which takes place by means of the roots, and 
movement of these juices in the plants themselves, should 
be considered as simple phenomena of capillarity, or im- 
bibition. 

At the commencement of spring, the sap rises from the 
roots to the leaves, through the central part of the trunk ; 
and at this time a liquid, called the sicccus proprius, or 
proper juice, whose composition is different from that of the 
sap (or succus communis,) passes in a contrary direction; 
that is, from the leaves through the cortical tissues to the 
roots. If we bore a hole to the centre of the trunk of a 
growing plant, we can collect a considerable quantity of 
sap, which is denser in proportion as it is taken higher up 
towards the leaves. If, on the contrary, we pass a ligature 

around the trunk, or if we re- 
move a circular layer of the 
bark, the swelling which we 
shall soon see formed above 
the knot or ring on the side of 
the leaves, will prove the ex- 
istence of the descending cur- 
rent of the proper juice. Hales 
has shown that the quantity of 
liquid absorbed by a plant in 
vegetation, increases in pro- 
portion with the superficies of 
its leaves ; a fact which he ex- 
plains by ascribing it to evapo- 
ration. 

This double movement of 
\/S^^^W^'^^/^ juices in the interior of vege* 

Hales's experiment to ascertain the tables, is a thing inexplicabfe 

by the mere forces of capil' 




force of the sap of the vine. 



LeCT. IV. ABSORPTION IN VEGETABLES. 95 

larity and imbibition. But there is also something more. 
You have all, doubtless, seen, that in cutting across a vine 
stem in the spring, there runs out an enormous quantity of 
liquid. Hales, by fixing to the top of the stem {Fig. 6. a, b) 
a mercurial guage (a, y) consisting of a curved glass tube 
{a, X, 3/, z,) containing mercury, and open at the other ex- 
tremity, observed that the mercury rose 38 inches (equal to 
43 feet 3J inches of water) higher in the longer open leg 
(y, z) of the tube than in the other leg [x ;) and this he 
ascribed to the force of the sap which came out of the 
stem and forced up the mercury. 

This force of impulsion, and the discharge of the liquid 
of the plant from a cut, are facts incompatible with the ef- 
fects of capillarity and imbibition. A liquid rising in a 
capillary tube, cannot overflow the tube by the effect of the 
same force which raises it. 

Dutrochet has demonstrated by a very simple experiment, 
that the force of impulsion which produces the ascension of 
the juice of a plant, has its seat in the ultimate extremities 
of the roots. This distinguished physiologist made succes- 
sive sections of the trunk of a vine, approaching each time 
nearer the roots ; and finally, he cut even the roots them- 
selves contained in the ground, and he observed that the^ 
flow of sap continued. One of the ultimate filaments of the 
rootlet, when plunged in water, also allowed the juice to 
escape from it. It is then in the spongelets that the force 
of impulsion resides. Dutrochet adds that he has disco- 
vered in the cortical cellules of the spongelet a liquid 
denser than water, and coagulable by nitric acid. He 
therefore, fancied that he had discovered in the spongelet, 
or rather in its cells, filled with a liquid denser than the 
water which surrounds them, a group of endosmometers ; 
hence the phenomenon of the ascent of the liquid in 
the plant becomes a case of endosmose. It is desirable, 



96 ABSORPTION AND EXHALATION. LeCT. IV. 

however, that the identity of these phenomena should be 
better demonstrated than it has been by Dutrochet's obser- 
vations. Be it as it may, the explanation given by this 
author is one which, in the present state of science, is the 
least improbable. 

How does the juice ascend in a plant whose roots have 
been removed, and whose lower extremity has been 
plunged in water ? The great height to which the liquid 
can ascend in the trunk of a tree, appears to be opposed to 
the explanation of the phenomenon by considering it as an 
effect of imbibition or of capillarity; phenomena which, 
we know, act within much narrower limits than those ob- 
served in the trunks of trees. Hales, finding that the quan- 
tity of sap which rises in a plant, was proportional to the 
superficies of its leaves, concluded that in consequence of 
the evaporation of the liquid contained in the superficial 
cells of the leaves, these absorbed, by capillary attraction? 
more liquid from the cells beneath, and that in this way a 
kind of suction gradually became propagated to the cut ex- 
tremity. 

By drying in different degrees some plants of the herb 
mercury [Mercunalis annua,) Dutrochet ascertained that 
they did not absorb proportionally to their degree of dry- 
ness ; for Gne of the plants which had lost a third of its 
weight by evaporation, absorbed much less than another 
which had only lost a tenth. Notwithstanding that the de- 
gree of dryness was greater, the absorption was less ; and 
yet the plant had not been sufficiently dried for its texture 
to have become altered. 

Evaporation or transpiration by the leaves is not then the 
cause of the ascent of a liquid in the stem of a plant 
plunged in water; or, what amounts to the same thing, it 
is not the cavities of the superficial cells which occasion the 
ascent of the juice. The latter is not effected without the 



LeCT. IV. ABSORPTION IN VEGETABLES. 97 

presence in the vegetable tissue of a certain quantity of 
water, which perhaps acts by adhesion to the new water 
which should rise, just as occurs with a sponge which is 
more rapidly impregnated with water when it has been pre- 
viously moistened than when it has been dried. Dutrochet 
also tried the effect of drying a plant, of allowing it to re- 
cover the water it had lost, and of plunging it again into 
that liquid ; and he found that, ahhough the water was re- 
stored, the ascent took place only when the plant had re* 
gained its original degree of turgescence. This turgescence 
of the leaf-cells takes place, according to Dutrochet, by an 
action of endosmose, in consequence of which the liquid 
is transpired by the leaves in an active manner, very different 
to that of a liquid which evaporates in the air. Lastly, I 
must remind you, that Dutrochet has demonstrated that the 
influence of light on the ascent of the sap in plants is exer- 
cised in respiration and in the fixation of oxygen in the 
vegetable tissue. 

The phenomenon of the ascent of liquids in plants does 
not, therefore, depend, solely on capillarity and imbibition* 
The cause resides principally in the roots, and in the next 
place in the leaves. It is probable that an action of endos- 
mose occurs in the extremity of the roots; and it is not^ 
unnatural to suppose that a similar cause acts in the move- 
ments of the chyle and lymph in the lymphatic and chyli^ 
ferous vessels-^a movement which continues some time 
after death. 



98 DIGESTION. LeCT V. 



LECTURE V. 

DIGESTION. 

Argument, — Digestion : Its final object; changes effected by it. 

Aliments are divisible into three classes. 

Class 1. Azotised substances ; albumiaie, Sbrine, and caseine. — Mulder's 
proteine theory ; digestion of azotised substances i gastric juice; move- 
ments of the stomach. 

Class 2. Amylaceous substances; starch,, sugar, and gum. — Digestion 
and conversion of starch into dextrine and sugar, and ultimately into 
lactic acid. Diabetes. 

Class 3. Fatty substances; fat and oil.-^Ofigin of fat in herbivora; 
division and liqaefaciion offals in the stomach; u.>e of the alkali of 
the bile and pancreatic juice; formation of an emulsion which is ab- 
sorbed ; agency of fat in the formation of celfe. 

Gases r>f the stomach and intestines. 

Inorganic substances found in the organism. 

Aliments. — The existence and preservation of an animal 
are dependent on the continual introduction into his body 
of certain substances, called aliments. These, which are 
usually solids, undergo in the digestive apparatus a series 
of modifications, by means o| which they are resolved into 
fgecal matters which are rejected, and other matters which 
mix with, and eventually become converted into, blood. 

Digestion. -^T\iQ ultimate object of digestion is the pre- 
servation of the integrity of the organism, by restoring to 
the blood the immediate principles which it is constantly 
losing during the act of nutrition. Reasoning leads us to 
suppose, that aJl parts of tbe organism undergo transforma- 



LeCT. V. DIGESTION. 99 

tion and renewal with greater or less rapidity. We are led 
to this conclusion by a number of experiments presented to 
us by experimental physiology, but which require to be 
varied and extended. 

The division of alimentary substances, the rendering of 
them soluble, and the consequent facilitation of their absorp- 
tion, are, in short, the changes which take place during 
digestion. Nothing can be more physical than a function 
which is exercised merely to modify the physical condition 
of matter. It is desirable, however, to see this character 
of digestion verified in its details. 

Before we begin to speak of the physico-chemical phe- 
nomena of this process, I must explain to you briefly some 
generalities . 

Varieties of Aliments. — All alimentary substances may, 
with respect to their composition, be reduced to three well- 
characterized classes : the first comprises substances which 
are azotised and neutral, namely, albumen, fibrine and case- 
ine ; the second includes fatty bodies ; and the third compre- 
hends gum, starch, and sugar, whose composition may 
perhaps be represented by water and carbon. Experiment 
has demonstrated, that the alimentary substances of the two 
latter classes are by themselves insufficient for the nourish- 
ment of an animal; and that they must always be conjoined 
with those of the first. 

We shall hereafter find that the alimentary substances of 
these classes serve distinct purposes in the animal economy. 

Azotised Substances. — With respect to the substances in- 
cluded in the first class : I cannot pass over in silence the 
important discoveries recently made by Mulder and 
Leibig. 

Albumen, fibrine, and caseine, are identical in their com- 
position ; the proportion of the carbon to azote, in all these 
three, being 8 equivalents of the farmer to 1 equivalent of 



100 AZOTISED SUBSTANCES. LeCT. V. 

the latter. They appear to differ from each other, merely 
in the small quantity of phosphorus and sulphur which they 
contain. If these two bodies be abstracted, there remains 
a principle common to the three, and which has been termed 
by Mulder, proteine ; the formula of which, as adopted by 
Liebig, is 

We must, then, regard these substances, although en- 
dowed with very different physical properties, as isomeric, 
and as modifications of proteine.* 

The other important fact discovered by Dumas and Liebig 
is, that vegetable albumen is identical with animal albumen; 
that, in the farina of the cereal grains there exists a substance 
analogous to caseine ; and, that in gluten there is a substance 
like animal fibrine. 

There is not, then, any essential difference between the 
aliments of the herbivorous, and those of the carnivorous 
animals, except that the first is drawn from plants, the 
second from animals. 

Since the composition of the blood, as well as the greater 

* Since the delivery of Matteucci's lectures Liebig's views respecting 
Mulder's theory of proteine have undergone an entire change, and he now 
declares this theory to be untenable and fallacious. In his Researches on 
the Chemistry of Food (1847) he observes, that "it now appears, as ihe re- 
suit of the more accurate investigations of Laskowski, Ruling, Verdeili 
Walther, and Fleitmann, that the amount of sulphur present in the blood 
constituents is three times, in many cases, four times, as great as the ap. 
pare^tly well-established analysis of the author of the proteine theory had 
indicated. It further appears, that a body, destitute of sulphur and having 
the composition of proteine, is not obtained by the methods given by 
Mulder ; that fibrine differs in composition from albumen ; that the albumen 
of effgs contains not less, but more sulphur than the albumen of the blood." 
(p. 27.) He aflso asserts that, " the existence of phosphorus, as an essential 
element of [some of] these substances [fibrine and albumen,] has not been 
in any way established." (p. 23.) — J. P. 



LeCT. V. AZOTISED SUBSTANCES. 101 

number of the animal tissues and fluids, is analogous to the 
organic neutral substances now referred to ; and since, more- 
over, in becoming part of the animal organism they undergo 
no change of chemical composition, but merely acquire 
during nutrition a new form, it is fair to assume that, in the 
act of digestion, the azotised neutral alimentary substances 
merely dissolve in order to pass, without any other altera- 
tion, into the blood. 

The isomerism of these substances is equally demonstrated 
by the beautiful discovery of Denis, that fibrine is converted 
into albumen by dissolving it in a saturated solution of nitre. 
This fact is the more curious, because it appears to hold 
good for the fibrine of venous blood only ; the fibrine of 
arterial blood, neither dissolving in a solution of this salt, 
nor becoming converted into albumen. Scherer has tried 
the effect of exposing the fibrine of venous blood to an at- 
mosphere of oxygen, and found that the oxygen was con- 
verted into carbonic acid, and the fibrine thereby lost its 
property of being convertible into albumen by a solution of 
nitre. 

Some physiological experiments have long since proved, 
that the digestion of similar alimentary substances is a purely 
physical act, which takes place independently of the living* 
organism. No one is ignorant of the celebrated experi- 
ments of our countryman Spallanzani : meat, gluten, and 
coagulated albumen, introduced into the stomach in perfo- 
rated metallic tubes, were dissolved and digested, as though 
they had been free in the stomach. This solution is effected^ 
as we shall presently find, by means of one of those actions 
of which we spoke in our first lecture, and which have been 
called catalytic or actions of contact. 

The recent experiments of Melsens, and especially those 
of Bernard and Barreswil, have shown, that the gastric juice 



102 DIGESTION. LeCT. V. 

contains a free acid, which shauld be lactic acid;* and that 
it holds in solution a peculiar substance called pepsine, which 
has been obtained in a sufficiently pure state. It is this 
same substance which has been lately examined by Payen, 
who termed it gasterase. The acidity of the gastric juice is 
greater or less, according to the quality of the aliments ; in 
an empty stomach, it is weaker: it augments by contact 
with food, and it has its maximum when the elements are 
composed of fibrine, albumen, &c. 

I here show you, in glasses, an infusion of pepsine to 
which a few drops of hydrochloric acid have been added. 
Into one of these small glasses has been put some coagu- 
lated albumen ; into another some fibrine. The vessels thus 
prepared have been placed for ten or twelve hours in an 
atmosphere heated to 30° centig.[= 86° Fahr.,] and the 
albumen and fibrine have already in a great measure disap- 
peared ; there remain only some small fragments, which are 
already transparent, on the edges, and which will shortly 
entirely disappear. If I neutralize the acid, and then eva- 
porate the solution, I can easily reproduce the albumen and 
fibrine, which have not been changed in their nature, but 
have merely dissolved by contact with the acid infusion of 
pepsine. This substance acts, therefore, in the solution of 
fibrine and albumen, as a body endowed with catalytic 
properties, and their solution is effected by an action of 
contact. 

It is only in the stomach, or by certain glands situated in 
the mucous membrane of this viscus, that the acid solution 
of pepsine, or the gastric juice is separated. I have tried 
the effect of placing pieces of the small or large intestine in 

* Liebig (Researches on the Chemistry of Food, p. 138.) infers from 
Lehmann's experiments, that the gastric juice contains lactic acid, and is 
similar to the juice of muscles. — J. P. 



LeCT. V. AZOTISED SUBSTANCES. 103 

a very weak solution of hydrochloric acid : the solution 
never acquired a solvent property ; it became gastric juice 
only by contact with the membrane of the stomach. 

The property with which pepsine is endowed, requires 
the constant presence of a free mineral organic acid. If, 
on the other hand, pepsine be dissolved in an alkaline 
liquid, its catalytic action becomes modified, as we shall 
hereafter find. 

Lastly, I may remark, that pepsine loses its properties 
and becomes insoluble, when heated beyond 50° centig. 
[= 122° Fahr.] 

Azotised neutral substances, dissolved in the stomach by 
the acid liquid, or by the catalytic action of pepsine, pass 
into the blood merely by the imbibition of the coats of the 
capillary blood-vessels of the stomach. Water, and 
coloured alcoholic drinks, introduced into the stomach, are 
also absorbed ; they do not pass beyond this viscus, nor are 
they to be found in the chyle ; yet they reach the blood. 
Bouchardat and Sandras fed animals with fibrine, coloured 
with either saffron or cochineal, and yet could never detect 
a trace of the colouring matter in the chyle. Moreover, 
animals fed on fibrine, and others which were kept fasting, 
yielded, when killed, chyle always of the same kind : the. 
contents of the intestines in no way differed, except, that 
in the animals fed on fibrine, a portion of the latter was 
found in the stomach incompletely dissolved. We know, 
also, from the celebrated experiments of Tiedman and 
Gmelin, that the quantity of fibrine contained in the lymph 
and chyle, after a long fast, is not less than that which is 
found there after digestion. The results are the same when 
coagulated albumen, gluten, and caseous matter, is em- 
ployed instead of fibrine. The digestion of these azotised 
neutral substances is, therefore, a mere solution, eflTected by 
an action of contact, and an absorption of this solution 



104 DIGESTION. LeCT. V. 

taking place chiefly in the stomach. Thus, then, nothing 
is more physical than this part of digestion. 

The mastication of aliments impregnated with a slightly 
alkaline and warm liquid, is an entirely physical operation 
similar to that which we practise in our laboratories in order 
to effect the division of a body, and thereby to promote its 
solution. 

The gastric juice which the stomach secretes, especially 
at the moment of digestion, is an infusion of pepsine in 
acidulated water ; and if we cause it to act on coagulated 
albumen, on fibrine or casein e, the solution of these sub- 
stances can be effected as well in a properly warmed re- 
ceiver as in the stomach. 

The movement of the walls of the stomach promotes the 
action of the infusion of pepsine upon the substances to be 
dissolved, just as all agitation aids the reaction of two dis- 
solved bodies, or the solution of a solid in a liquid. 

This movement of the walls of the stomach, is also of as- 
sistance in another way : by incessantly renewing the points 
of contact between them and the matter which they contain, 
the absorption of the liquid portion of this substance is ef- 
fected more readily. The influence which the division of 
the eight pair of nerves has in disturbing digestion, is 
ascribable, in part, to the cessation of these movements, 
which are dependent on the action of the nerves. More- 
over, their section produces a great disturbance in other 
functions indispensable to the integrity of the animal 
economy. 

Amylaceous Substances. — I shall now speak of the di- 
gestion of amylaceous matters, a subject on which we have 
been much enlightened by the beautiful experiment of San- 
dras and Bouchardat. This experiment is very easily per- 
formed. A few drops of pancreatic juice, added to some 
boiled starch or starch jelly, at the temperature of -|- 35° to 



LeCT. V. AMYLACEOUS SUBSTANCES. 105 

40° centig. [= 95° to 104° Fahr.] shortly dissolved it ; 
the liquid became transparent, and, subsequently, every 
trace of starch disappeared. 

The same effect is produced if, instead of the pancreatic 
fluid, we employ a piece of the pancreas of the pigeon, or 
of some other animal. I shall use the pancreas of a pigeon. 
Having pounded it, I add some of the pounded substance 
to the fecula, and heat the mixture to 40° centig. [= 104° 
Fahr.] The fecula dissolves, and is converted into dextrine 
or sugar. 

This is the state to which starchy substances are re- 
duced before they are absorbed. There must exist, then, 
in the juice of the pancreas, and perhaps, also, as Magendie 
asserts, in the saliva, a substance which acts upon starch 
like diastase. 

It is singular that this action requires the presence of a free 
alkali ; for, if the pancreatic juice be acidulated, it ceases 
to act on starch, but, according to Bernard and Barreswil, 
acquires the property of acting upon the neutral azotised 
substances. We must, therefore, conclude, that a single 
organic substance has the property of dissolving fecula and 
the azotised neutral matters, provided that we add, when 
we act on the first, a free alkali, and when on the second, 
a free acid. 

We have now to ascertain whether the starch thus con- 
verted into dextrine and sugar, by the saliva and pancreatic 
juice, passes in this state into the blood, or whether it is 
converted into lactic acid. 

It is in the blood of some diabetic patients only, that su- 
gar has been found. The hypothesis, that the conversion 
of starch into dextrine and sugar terminates in the formation 
of lactic acid, which is absorbed and passed into the circu- 
lation, seems to be more in accordance with facts. We 
must not forget the important discovery made by Fremy, 



106 DIGESTION. LeCT. V. 

of the property which certain animal membranes acquire 
when kept for some time in contact with water, of convert- 
ing large quantities of sugar into lactic acid. 

These same azotised substances, which, under certain 
conditions, excite the lactic fermentations, when taken in 
another state, which I shall call a more advanced stage of 
transformation, and the nature of which up to the present 
we are ignorant of, cease to produce lactic acid by their 
action upon sugar ; and, on the contrary, they aid alcoholic 
fermentation, by transforming the sugar into carbonic acid 
and alcohol. Moreover, we know that a solution of sugar 
injected into the veins of an animal, soon makes its appear- 
ance in the urine. 

From our knowledge of organic chemistry, and the well 
known results obtained by actions of contact, we may con- 
clude that starch is convertible, in the bowels, into lactic 
acid, by first passing into the intermediate states of dextrine 
and sugar. 

It is neither unreasonable, nor in opposition to the pre- 
sent state of knowledge, to suppose that a portion of sugar, 
into which starch has been converted, not only suffers in the 
intestines the lactic fermentation, but also undergoes some 
other transformation there, analogous to that, in the midst 
of which we now know the infusory animalcules are pro- 
duced. 

The recent experiments of Gruby and Delafond prove 
beyond doubt, that very large numbers of these animalcules 
are especially found in the stomachs of herbivora. 

Diabetes. — I cannot close this subject without offering a 
few remarks on the researches which have been made to 
discover • the cause and the curative treatment of dia- 
betes. 

Bouchardat first broached the opinion, which has since 
been generally adopted, that in this malady starch was 



LeCT. V. DIABETES. 107 

converted in the intestines into sugar, which passed into 
the blood and urine. 

Hence, a diet entirely excluding starch, and composed 
principally of neutral azotised substances, has been pre- 
scribed as a remedy for diabetes ; and cases are mentioned 
in which by this means a cure has been effected. 

Nevertheless, all that we have now said is contradicted 
by the numerous experiments of Dr. Capezzuoli, w^hich tend 
to prove, that the quantity of sugar found in the urine of 
diabetic patients is not at all proportionate to that of fecula 
taken as aliment; and, that even under a diet composed 
exclusively of neutral azotised substances, the same amount 
of sugar is found as when the aliments contained much 
fecula.* 

Dr. Capezzuoli found sugar in the contents of the in- 
testines, and in the matters vomited by diabetic patients? 
after a meal of starchy substances exclusively. But the 
quantity of sugar was the same in a healthy man as in a 
diabetic patient. This fact must always possess great im- 
portance for the theory of digestion ; the transformation 
of fecula into sugar being thus demonstrated by experi- 
ment. 

Lastly, Dr. Capezzuoli found traces of sugar in the blood, 
and in the contents of an abscess in a diabetic patient. The 
abundant production of grape-sugar in these diseases, which 
appear to be always accompanied with great wasting, re- 
mains yet to be accounted for. 

Fatty Substances, — We must, lastly, consider the di- 

* That by the exclusive use of animal food the quantity of sugar in the 
urine of diabetic patients may be greatly reduced, is a fact which I myself, 
in common with many others, have repeatedly noticed. But, as I have 
elsewhere observed (A Treatise on Food and Diet, p. 500.) " I have never 
seen this secretion entirely loose its saccharine condition by even the most 
rigorous adoption of animal diet." — J. P. 



108 DIGESTION. LeCT. V. 

gestion of fatty matters, which are taken in very large 
quantities into the stomachs of the carnivora, and which, 
undergoing scarcely any modifications in their composition, 
are conveyed into the adipose tissues. 

For this purpose, I must say a few words on the impor- 
tant question lately mooted by chemists, respecting the ori- 
gin of fat in herbivorous animals. 

Liebig maintains, that it is produced by means of a 
transformation of fecula. This looses a portion of its oxy- 
gen, which is expelled from the organism in combination 
with carbon. 

Dumas, Boussingault, and Payen, on the contrary, be- 
lieve that the quantity of fatty matter in hay, beet-root, and 
straw, is sufficient to account for the amount of fat found 
in animals fed with these substances. Boussingault has de- 
monstrated the truth of this opinion by observations made 
on a cow. He found, that whilst the quantity of fatty mat- 
ter existing in the aliments on which she was nourished 
weighed 1614 grammes, the amount found in her milk was 
only 1413 grammes ; showing an excess of .201 grammes 
of the fat contained in the aliments, over that obtained from 
the products of the animal. 

The same chemist also found, by means of experiments 
made on pigs and geese, that in these animals a much larger 
quantity of fat is produced than is contained in their food : 
and Persoz has arrived at the same conclusion. 

It cannot, therefore, be denied that the animal economy 
possesses the faculty of transforming a portion of substances 
used for nourishment into fat. Chemical knowledge is of 
no assistance to us, in this instance, in explaining this trans- 
formation.* 

* Chemists have succeeded in converting sugar into fatty matter. 
" When a solution of sugar is left to ferment, at a high temperature, in 



LeCT. V. FATTY SUBSTANCES. 109 

On the other hand, it has been proved, by a great num- 
ber of physiological observations, that in animals fed on 
fat, the chyle is more abundant and milky than usual, and 
that these same substances may be extracted from it. More- 
over, when submitted to the microscope, small globules of 
fat are perceived in it. 

The experiments of Sandras and Bouchardat have proved 
this fact, beyond doubt. These chemists fed animals with 
oil of sweet almonds, and found this substance in the chyle ; 
and they obtained a like result with suet. When wax was 
employed, they found only a small quantity of this sub- 
stance in the chyle ; but which, however, was augmented 
when the wax was introduced in a state of solution in oil. 

These gentlemen have also examined the contents of the 
stomach and intestines of animals fed exclusively upon 
fat ; and they found in the stomach a large portion of 
fat, solidifiable by cold, and contained in a very acid liquor. 
There was, also, both in the large and small intestines, a 
kind of thick pap [bouillie,) from which ether extracted a 
large quantity of fat. 

It results from these facts, of the truth of which I have 
satisfied myself, that fatty matters suffer no change in the 
stomach, and that they pass into the intestines without 
having undergone any modifications except being divided, 
and liquefied by the heat of this organ. Moreover, by 
causing the gastric juice to act on fat out of the stomach, 
no change appears to be effected in it. 

The alkali of the bile and of the pancreatic juice satu- 
rate, in the intestines, the acid of the gastric juice. Here, 

contact with putrefying caseine, there is separated from the elements of 
the sugar, if the oxygen of the air be excluded, a certain quantity of car- 
bonic acid and of hydrogen gases, and we obtain, as is now well known, 
a fatty or oily acid, the butyric acid,'''* (Liebig's Animal Chemistry, p. 
113. 3d ed. 18460— J. P. 



110 DIGESTION. LeCT. V. 

then, is a fresh proof that, in the intestines, the solvent ac- 
tion on the neutral azotised substances ceases. 

Absorption of Fat. — It is difficult to determine precisely 
by analogies derived from chemistry, what becomes of the 
fatty substances after they have passed out of the stomach. 
It is certain that they are there absorbed, and that the chy- 
liferous vessels may be considered as almost exclusively 
charged with this function. 

Here are some experiments by means of which I have 
endeavoured to diminish the obscurity which hangs over 
this part of the digestive process. I put into a matrass a 
solution of 300 grammes [= 9 oz. 132 grs. troy] of dis- 
tilled water, It^ grammes [about 20 grains troy] of caustic 
potash. This solution has not any perceptible alkaline 
taste, and acts very feebly on litmus paper ; it is a liquid 
whose alkalinity is about equal to that of the lymph and 
chyle. By means of a salt water bath, I expose the ma- 
trass to a temperature of from 35° to 40° centig. [== 95° 
to 104° Fahr.;] I then add some drops of olive oil and 
shake the mixture; it instantly becomes so milky that it 
might be mistaken for milk itself. The liquid thus ob- 
tained, when left to itself, preserves its analogy to milk, 
and separates into two layers, the one more opaque at the 
top, in which are evidently small globules of fatty matter ; 
the other, below, and less opaque, although still having a 
milky aspect. I have filled a piece of intestine with this 
species of emulsion, and plunged it into the alkaline solu- 
tion already described, whose temperature was maintained 
at from + 35° to 40° centigs. [= 95° to 104° Fahr.] 
After some time, the latter becomes turbid and acquires the 
characters of the interior emulsion. We, therefore, pre- 
sume, that a portion of the emulsion has passed through the 
membrane and become diffused externally. 

I may mention to you another experiment which appears 



Lect. V. 



ABSORPTION OF FAT. 



Ill 



to me still more conclusive. I filled an endosmometer with a 
ver}' weak alkaline solution, and plunged it into the emul- 
sion. The membrane employed was, as usual, ox bladder, 
and the two liquids were at the temperature of -f 30° centig. 
at the commencement of the experiment. Endosmose took 
place; the emulsion passed into the alkaline solution; and 
the liquid rose in the tube to the height of 30 millimeters 
in a very short time. 

These physical phenomena, which, although they do not 
explain all the peculiarities ^f the digestion of fatty sub- 
stances, nevertheless contribute to render them less ob- 
scure. The chyliferous vessels, which terminate in closed 

Fig. 7. 





Extremity of intestinal villus, seen at a, during absorption, and showing absorbent 
cells and lacteal trunks, distended with chyle; at b, during interval of digestion, 
showing peripheral network of lacteals, with granular germs of absorbent cells, as yet 
undeveloped, lying between them. 



or blind extremities {en cul-de-sac^) and are enveloped by 
intestinal mucus, are, especially in a fasting animal, filled 
wdth an alkaline liquid, very analogous to lymph. After 
digestion, particularly when the animal has been fed ©n 
fatty substances, the liquid of the chyliferous vessels dififers 
from what it was previously, merely by the addition of fatty 
corpuscles, which give it the milky appearance. It is na- 
tural to suppose, that this chemical affinity, which produces 
the milky liquid in the mixture of the alkaline solution and 
oil, is also exerted through the membrane of the chyliferous 
vessels, which certainly imbibes as much of the alkaline 



112 DIGESTION. LeCT. V. 

solution as of the milky liquid, formed by the action of the 
alkali on the fatty bodies. 

The phenomena of endosmose, of which I have spoken, 
may also be admitted, with great probability, as one of the 
causes which produce absorption by the chyliferous vessels. 
It is certain, that absorption could not take place, if the 
inner sides of the intestines were not bathed with some 
liquid, for which the fatty bodies had some affinity. 

It is easy to demonstrate, by experiments, that the alka- 
line condition of the intestin^ coats favours this absorption. 
Fill two funnels with sand, equally shaken down in each. 
Pour into one, pure water, into the other, an alkaline 
solution ; when the liquids have filtered through, pour an 
equal quantity of oil on each filter. For several hours, the 
oil will remain upon the surface of the sand, which has been 
moistened with pure water; whilst in the other funnel, in 
which the sand has been moistened with the alkaline solu- 
tion, the oil will rapidly disappear by imbibition. 

The neutral azotised substances which pass into the 
blood, after having been dissolved by the gastric juice; 
would rapidly destroy the neutral or slightly alkaline con- 
dition necessary to the preservation of the qualities of the 
blood ; but the alkali of the chyle, of the lymph, of the bile, 
and of the pancreatic fluid, preserve the neutrality of it. 

Origin of Cells. — The chyle and the lymph hold in sus- 
pension a great number of small grains, which are from 1 
to 2 thousandths of a line in diameter, and which appear to 
be formed of a fatty substance, enveloped in a membrane, 
which is supposed to consist of a substance analogous to 
proteine. These same granulations exist in yolk of egg, in 
the milk, chyle, lymph, and in all the liquids exuded in 
pathological cases, or destined for new formations. These 
elementary granulations have been seen to unite and form 
a globule, a cell analogous to blood-cells ; hence, they have 



LeCT. V. ORIGIN OF CELLS. 113 

been regarded as the morphological elements of all animal 
tissues. 

Recently, Donne observed, by injecting milk into the 
blood-vessels, that the globules of milk disappeared, after 
some time, by becoming covered with an albuminous layer, 
like a bladder ; that they then become reduced to the con- 
dition of white globules of the blood, which, finally also 
disappeared, being probably transformed into red globules. 
Afterwards, all the blood re-acquired the appearance which 
it had before the milk had been injected into it. 

The organic element seems, then, to be reduced to a 
vesicle consisting of a layer of albumen, collected together 
and organized around a nucleus^ formed principally of a 
fatty substance. 

I can bear testimony to an important experiment made 
by Ascherson : it consists in putting a fatty liquid in con- 
tact with albumen. This latter instantly coagulates, as you 
here see. If you mix them together, and put a drop of 
the mixture under the microscope, you will perceive a 
group of vesicles, each formed of a granule of oil, enve- 
loped by an albuminous membrane, in some degree coagu- 
lated, and, it appears, like what the real adipose cell would 
do, on the stage of the microscope. We can see this still 
better, by putting, on a plate of glass, a drop of oil, and one 
of albumen, and slowly bringing them in contact: it is 
curious to observe, by the microscope, the almost instanta- 
neous formation of a very delicate and elastic membrane, 
which soon acquires numerous folds. Ascherson has 
proved, that this formation, produced by albumen and oil, 
is really of a cellular nature. By adding a little water to a 
drop of this formation, he saw the cells swell up, and at the 
same time some small drops of oil escaped. By using di- 
luted acetic acid instead of water, the cellules appeared to 
him to become so voluminous, that they burst. In oil, on 
8 



114 DIGESTION. LeCT. V. 

the contrary, they became compressed, and diminished in 
size.""^ 

Evidently these facts, which nevertheless require to be 
varied and extended, belong to the phenomenon of endos- 
mose, and cannot be comprehended without admitting the 
cellular formation. Here, then, is a physico-chemical ope- 
ration, which may lead to the discovery of the formation of 
elementary granulations. Fatty substances, and combina- 
tions of proteine, are constantly introd^uced into the or- 
ganism : they are met with in all animal tissues ; the glo- 
bules of fat, which pass into the chyliferous tubes, and are 
there found in an albuminous liquid, must soon become 
enveloped by analogous membranes; and ought, for this 
reason, to form vesicles resembling those which microscopic 
observation discovers in the chyle, the lymph, and the 
blood. 

Gases in the Stomach and Intestines. — In concluding this 
lecture, I have only to add a few words on the gas contained 
in the stomach and intestines, as w^ell as on the inorganic 
substances, which form, more or less directly, an integral 
part of the animal organism. 

Observation has proved, that oxygen is scarcely ever met 
wnth in the gases of the stomach, and more especially in 
those of the intestines ; but that these are principally com- 
posed of azote, carbonic acid, a certain quantity of car- 
buretted hydrogen, and sometimes traces of sulphuretted 

* Ascherson's hypothesis of the formation of cells is quite inadmissible. 
"Caseine, albumen, and fibrine, in solution, may have the property of se- 
parating fat into globules; they may form a layer or membrane around 
a drop of oil, and so prevent the oil from running togeiher. This pro- 
perty is possessed by gum arabic also, and, even though it were possessed 
by no other substance whatever, a, passive layer of a solid substance around 
a fluid is entirely differentfrom an active membrane, from which manifold 
actions proceed in organic nature. Such theories tell us nothing more 
than does the formation of froth in soap water." — (Mulder.) — J. P. 



LeCT. V. INORGANIC CONSTITUENTS. 115 

hydrogen. Evidently a large quantity of atmospheric air is 
introduced into the stomach : that is to say, it is swallowed 
with the food. The oxygen of the air disappears in the 
stomach, perhaps by filtration through the membranes, and 
reaches the blood ; or, what is still more probable, by taking 
part in those modifications which we know occur in order 
to transform the azotised albuminous substances into fer- 
ment. Carbonic acid appears very abundantly developed 
in this case ; and the enormous volumes of this gas, which 
is disengaged in some animals fed on fresh and moist herbs, 
may be here referred to. 

It is curious to observe, that the production and disap- 
pearance of this abundant quantity of gas in the stomach 
and intestines, take place and succeed each other sometimes 
with so much rapidity, that one cannot have recourse to 
chemical reactions to explain them. The presence of hy- 
drogen cannot, at present, be referred to any of the physico- 
chemical changes which we have seen to take place during 
digestion. 

I have shown, by experiment, that oxygen is not neces- 
sary to the solvent action which the gastric juice exercises 
on fibrine and coagulated albumen, as Liebig seems to sup- 
pose. A piece of the stomach of a pig was put, along with 
some fibrine and coagulated albumen, into slightly acidu- 
lated water; the water had boiled for several hours, and the 
prepared liquid was covered with a thick film of oil. The 
fibrine and albumen were dissolved in this bath quite as 
well as in another similar one which was left in contact 
with the air. 

Inorganic Constituents of the Body. — The inorganic sub- 
stances found in the organism, have been evidently intro- 
duced from without, and formed part of the aliments : they 
cannot reach the blood unless they have been dissolved in 
water, and in the gastric juice of the stomach. Whatever 



116 DIGESTION. LeCT. V. 

is incapable of fulfilling these conditions, is necessarily re- 
jected with the excrements. Physicians should never forget 
this truth, in selecting and preparing substances for admi- 
nistration to their patients. Experience has now proved, 
that it is by no means surprising if large doses of certain 
inorganic salts introduced into the stomach do not produce 
any effect ; for they are rejected in the excrementitious 
matters. 



LeCT. VI. RESPIRATION. 117 



LECTURE VI. 

RESPIRATION. — GASEOUS ENDOSMOSE. 

Argument. — Phenomena of respiration. Respiratory organs in different 
class of animals. Mechanism of respiration ; inspiration; expiration. 

Changes produced in the air by respiration; changes effected by fishes in 
the air dissolved in the water in which they live. Respiration is both 
pulmonary and cutaneous. 

Changes produced in the organism by respiration; arterialization of the 
blood. Respiration of gases. 

Physico-chemical nature of the process of respiration ; changes produced 
by atmospheric oxygen in venous blood drawn from an animal ; nature 
of the changes ; experiments of Magnus ; atmospheric oxygen acts on 
blood through membrane ; the process is, perhaps, gaseous endosmose ; 
diffusion of gases ; Valentin and Brunner's researches. 

Conclusions. 

Phenomena of Respiration. — The action of the oxygen of 
the atmospheric air on venous blood ; — the changes pro- 
duced in the air by its introduction into the pulmonary 
cells ; — and the modifications effected in the blood which 
traverses the capillary network, on the delicate walls of the 
bronchial vesicles ; — are the principle phenomena which 
constitute the function of respiration, and which will form 
the subject of the present lecture. 

Organs of Respiration. — No animal exists, — even amongst 
those possessing the lowest degree of organization,— whose 
life is not essentially connected with those modifications 
which atmospheric oxygen produces in its substance. The 
organs, by means of which this action takes place, are more 




118 RESPIRATION. LeCT. VI. 

or less developed, and have diversities of form and struc- 
ture, adapting them to the medium in which the animal 
usually lives. 

In fishes, for example, the organ of respiration is a mu- 
pj 8. cous membrane, provided with many 

folds, and divided into filaments, or 
lamellse, and abounding in blood-ves- 
sels. It is always in contact with the 
water, which is introduced through 
the mouth, and expelled by the 
branchial fissures. In these animals 
every thing is arranged so as to give 
the greatest possible extent of sur- 
face for the contact of the water, in 
One of the arborescent pro- ^^^ich the atmosphcric air is dis- 

cesses, forming the gilts of • i i i n x 

Doris Johnstoni, separated SOlvcd, With the' VaSCUlar Walls. In 

and enlarged. |-}^g common ray, the branchiae or 

gills have a surface of 2250 square inches. 

In reptiles, birds, and mammals, the respiratory organ 
consists of an expansion of the bronchial tubes, which ramify 
like a tree, and whose very delicate extremities terminate 
by a large number of spheroidal vesicles placed side by 
side, and surrounded by small blood vessels. The respira- 
tion of some reptiles, at least during the first period of their 
existence, is both that of fishes and mammals: hence they 
have at the same time both branchiae and lungs. 

Mechanism of Respiration. — The movements necessary to 
this function are partly voluntary, partly involuntary. They 
may be reduced to two acts, one by w^hich air is introduced, 
another by which it is expelled. All the air passages dilate 
during inspiration^ all contract during expiration. The 
combined action of the muscular force, and of the elasticity 
of the osseous and cartilaginous parts of the thorax, as well 
as of that which is peculiar to the walls of the air vesicles, 



LeCT. VI. MECHANISM OF RESPIRATION. 1 19 

and, lastly, the physical properties of the air itself, are the 
causes of the respiratory movements. 

The whole thoracic cavity dilates during inspiration, and 
the air rushes into the bronchia ; whereas during expiration, 
this cavity contracts, and the cells of the lungs, being 
elastic, resume their primitive volume, whereby the air, be- 
ing thus compressed, and possessing an elasticity more or 
less great, in proportion to the degree of heat communicated 
to it by the lungs, is expelled. The simple action of a pair 
of bellows shows you the whole mechanism of the respira- 
tory movements. 

In fishes, this motion takes place without the co-opera- 
tion of the ribs. The branchial arches open, the lamellag 
separate, and the contact between them and the water thereby 
takes place. They then close, and the water escapes by 
the branchial fissure, which remains open until the opercu- 
lum falls. 

In the lower animals respiration is less energetic, and the 
motions of inspiration are almost involuntary. In the an- 
nelides and mollusca, the current of water, in which the air 
is dissolved, seems aided by the vibratile movements of 
the cilia placed on the branchiae of these animals. 

Air respired. — A man, at one respiration, introduces into 
his lungs about 20 cubic inches, or rather more than 
half an imperial pint, of atmospheric air ; the air expired 
contains usually from 3 to 5 per cent, of carbonic acid ; but, 
after a very deep expiration, as much as 6 or 8 per cent. 
At the same time the inspired air has lost from 4 to 6 per 
cent, of its oxygen. 

The numbers I have quoted have been selected from 
many others as being those which appear most worthy of 
confidence. From them it is easy to calculate the quantity 
of oxygen which a man absorbs by respiration in a day ; 
assuming that he makes from 15 to 20 inspirations in a mi' 



120 RESPIRATION. LeCT. VL 

nute. According to Lavoisier and Seguin, the oxygen con- 
sumed in the respiration by an adult man, weighs 1015 
grammes [about 15,675 troy grains.] The quantity which 
disappears during respiration in man and birds is, by volume, 
nearly equal to that of the carbonic acid evolved. Some 
very accurate observers have found that the volume of oxy- 
gen absorbed is greater than that of the carbonic acid pro- 
duced. This difference is especially manifest in the carni- 
vora, in which Dulong found that the oxygen which disap- 
pears is sometimes double the volume of the carbonic acid 
formed. 

By making an animal respire in a definite volume of air, 
Dulong and Despretz have proved beyond question, that a 
remarkable quantity of azote is always produced. This 
fact show^s that the excess of azote thus exhaled comes from 
the aliments, and perhaps also from that azote w^hich, as 
we stated, is found in the stomach and intestines as the re- 
sidue of the air introduced with the food. And if the quan- 
tity of azote contained in atmospheric air be invariable, 
Boussingault has demonstrated that this arises from the fact 
that some plants absorb this gas. 

The same changes which respiration produces in the com- 
position of atmospheric air, also take place in the air dis- 
solved in water. We know, that in both common and sea 
water there exists, dissolvied, a certain quantity of atmo- 
spheric air, which may be disengaged by ebullition, by 
bringing it in contact with some other gases, or by putting 
the water in vacuo. These phenomena, W'hich are alto- 
gether physical, take place, according to the well known 
laws of the absorption of gases by liquids, discovered by 
Dalton. 

The experiments of Morren, likewise prove that a certain 
quantity of carbonic acid is dissolved in these waters, and 
which seems to vary in the inverse ratio of the oxygen 



Lect. VL air respired. 121 

which also exists there. The proportion of oxygen con- 
tained in a definite volume of air dissolved in water, exceeds 
that met with in atmospheric air. Humboldt and Gay 
Lussac found in air obtained from fresh water 32 per cent, 
of oxygen. According to Morren, the quantity of oxygen 
in sea water appears to vary at different hours of the day, 
and is at a maximum about noon ; the reverse holds good 
for the carbonic acid. 

Fishes absorb a portion of this dissolved oxygen, and 
yield up carbonic acid, which is absorbed by the water ; and 
it is only by the continued solution of fresh portions of at- 
mospheric air that the respiration of these animals can go on. 
This is the reason why they quickly die in water deprived 
of air by ebullition, or in water covered with oil. 

I may here mention an experiment which I made some 
time ago on the respiration of the torpedo. The air dis- 
solved in the water of the Adriatic, taken near the shore, 
consists, in 100 parts, of 11 carbonic acid, of 60-5 azote, 
and 29*5 oxygen. A large torpedo was kept for 45 minutes 
in about a gallon of this water. The animal was frequently 
excited, gave many shocks, and soon died. The air dis- 
solved in the water, did not yield a trace of oxygen, but 
contained 36 per cent, of carbonic acid, the remaining parts 
in the hundred being azote. 

Experience has proved, that these changes in atmospheric 
air, effected by contact with a living animal, take place not 
only in the lungs, but also, in different degrees, at the entire 
surface of the body of the animaL Frogs, confined in a 
definite quantity of air, and either deprived of their lungs 
or in some way prevented from carrying on pulmonary respi- 
ration, continue to live. After some time, it is found that 
a portion of the oxygen has disappeared, and has been re- 
placed by carbonic acid. 

Humboldt and Provencal observed, that tench live with- 



122 RESPIRATION. LeCT. VI. 

out much suffering, though their heads and branchiae were 
out of water, and their bodies alone immersed. Spallanzani 
and Edwards have farther proved, that cutaneous respiration 
is indispensable in the batrachians; so that frogs can live 
several days without lungs, but on the other hand, they 
perish in a few hours if they are flayed or have their skin 
varnished. A snake whose whole body is varnished soon 
dies. Sorg immersed one of his arms in oxygen for four 
hours ; at the expiration of this time he found that about 
two-thirds of the gas had disappeared. Davy analyzed the 
air which had been injected into the pleura of a dog, and 
found that after a short time it yielded only slight traces of 
oxygen. 

The mechanism of respiration, and the chemical changes 
which accompany this function, take place, therefore, in all 
animals in the same manner. Oxygen disappears in the 
respiratory organs, and, at the same time, carbonic acid is 
exhaled from them: there is more azote in the expired air 
than in the air which was inspired ; the volume of the 
carbonic acid evolved is never greater than that of the oxy- 
gen absorbed; and in certain animals it is one half less than 
the latter, and the returned air is saturated with aqueous 
vapour. 

Effects of Respiration. — Whilst the respiratory act is 
effecting the changes in the atmospheric air, which I have 
now described, what happens in the organism? None of 
you can be ignorant of the fact that, during respiration, the 
venous blood, being carried to the lungs, loses its black- 
ness and acquires a bright vermilion colour, becomes arte- 
rial, is returned to the heart, and from this organ is sent to 
all parts of the body. The interruption of this transforma- 
tion occasions speedy death. 

I could adduce a great number of experiments to prove, 
that the change of the venous into arterial blood takes place 



LeCT. VI. EFFECTS OF RESPIRATION. 123 

in the lungs during the act of respiration. Bichat divided 
both the trachea and arteries of a dog, and immediately 
applied a stop cock to the opening of each of these vessels. 
By closing the stop cock of the trachea, shortly after an in- 
spiration, the arterial blood became blackish, and before it 
had flowed a minute was completely venous. On repeat- 
ing the experiment, and closing the stop cock as soon as 
possible after an expiration, the arterial blood flowed for a 
few seconds, and was of a black colour. When we re- 
moved the air from the lungs, by means of an air-pump, 
the blood immediately issued from the artery, black ; when, 
on the contrary, we threw a little air into the lungs, the 
blood preserved for a longer time its vermilion colour. By 
carefully opening, from time to time, the stop cock of the 
trachea, an alternate shower of red and black blood was 
obtained. 

Here is a rabbit, to the trachea of which a stop cock is 
fixed: observe the peritoneum which has been exposed. 
You perceive that the red colour of these vessels changes 
to a deep red when the stop cock is kept closed for a few 
moments, but returns to its natural tint when the stop cock 
is re-opened. In asphyxiated animals the tissues of all parts 
of the body, the kidneys, the muscles, the tongue, and the 
lips, assume a blackish colour. If the two pneumo-gastric 
nerves of an animal be divided, the respiratory movements 
soon become disturbed ; and at the same time all the blood 
preserves its black colour, and the lips, the nostrils, and the 
pharynx of the animal lose their red tint. 

If, instead of introducing atmospheric air into the lungs 
of an animal, we make it breathe azote, carburetted hydro- 
gen, pure hydrogen, carbonic oxide, carbonic acid, binoxide 
of azote, or sulphuretted hydrogen, death takes place more 
or less rapidly, and the blood of every part of the body is 
found black. Besides atmospheric air, oxygen and protox- 



124 RESPIRATION LeCT. VI. 

ide of azote are capable of maintaining respiration for a few 
minutes. Perhaps, in oxygen gas this function would be 
maintained for a considerable time, were it not that by 
breathing this gas the respiratory movements become more 
frequent, the arterial pulsations quicker, and the blood every 
where acquires a very bright red colour. In protoxide of 
azote respiration may be continued for a few minutes with- 
out any serious inconvenience ; but, as in the case of oxy- 
gen, the respiratory movement is accelerated, the cerebral 
functions become disturbed, and a kind of drunkenness 
ensues. 

We are now acquainted with the phenomena which take 
place during respiration, both in the air itself and in the 
organism ; oxygen is absorbed, carbonic acid is exhaled, 
black venous blood is changed into red arterial blood, and 
these two modifications occur in the same organ, where, 
from its peculiar structure, the atmospheric air, which yields 
up its oxygen, and the venous blood which becomes red, 
are nearly in contact, or separated only by an extremely 
thin membrane. 

Respiration is a physico-chemical process. — Are these mo- 
difications of the air and the blood, phenomena which occur 
in living beings only ? Do we find, that any changes ana- 
logous to those which happen during respiration, ever take 
place between atmospheric oxygen and venous blood drawn 
from a living being ? The most simple experiment will 
soon answer these queries, and leave no doubt in your minds 
of the absolutely physico-chemical nature of this function. 

Here I have a mass of blood which has been coagulated 
for several hours : you perceive that its surface is red, 
while that of the piece which I cut off' is blackish ; but be- 
fore many minutes have elapsed it becomes red. I direct 
some carbonic acid upon the red surface of this clot, and 
it becomes almost immediately black. I pass a current of 



LeCT. VI. NATURE OF ARTERIALIZATION. 125 

this gas through a liquid formed of blood dissolved in 
water, and you find that it will soon become black. This 
blackish liquid, being placed in a flask filled with oxygen, 
and agitated for a few moments, looses its deep colour and 
acquires a vermilion tint. Sulphuretted hydrogen is the 
only body, which having acted on the blood, even in very 
small quantities, renders this fluid incapable of being arte- 
rialized by oxygen. 

Since the time of Priestley it has been known, that if 
blood, which has become blackish from the action of car- 
bonic acid, be put into a moist bladder which is placed in 
contact with oxygen, the blood again becomes red, the 
interposed membrane not preventing the change of colour. 

It is then proved, by experiment, that the, change from 
black to red in the colour of the blood, which constantly 
accompanies the introduction of oxygen into the air ves- 
sels of living animals, under circumstances identical with 
those which I have pointed out, is a phenomenon entirely 
physico-chemical, and consists in the action of oxygen 
upon a liquid which has its origin in the living organism. 

JYature of Arterialization. — What, then, is the nature of 
this change ? What are the laws which govern it? Here 
are the details which must still engage us ; and in such 
investigations we shall rely on the splendid researches of 
Magnus. 

If we receive the venous blood, which escapes from an 
aperture in the "vein of a living animal, in a vessel contain- 
ing pure hydrogen gas, and shake the two together, we 
shall find in the vessel some carbonic acid. This certainly 
cannot be the result of the chemical combination of hy- 
drogen with the elements of the blood ; nor can it be sup- 
posed that the acid was expelled from the blood by the 
affinity of hydrogen, for the body with which we may fancy 
the carbonic acid was combined. The carbonio acid, 



126 RESPIRATION. LecT. VI. 

therefore, must have been dissolved in the blood, and have 
been disengaged by hydrogen, by the action which one gas 
has on another of a different nature, dissolved in a liquid. 
If we have substituted arterial for venous blood, we should 
have obtained a smaller quantity of carbonic acid. If we 
substitute azote for hydrogen, there is also disengaged, by 
the contact of that gas with the blood, carbonic acid, the 
quantity of which from venous blood should be more than 
double that obtained from arterial blood. By this method 
we not only obtain carbonic acid, but also some oxygen 
and azote, which are disengaged along with it. The re- 
sults obtained by Magnus are so deserving of confidence 
and so important, that I think it my duty to make you ac- 
quainted with his numerical results. He extracted and 
analyzed the gases dissolved in the blood, by means of a 
peculiar apparatus, by the aid of which he made a vacuum 
over the blood itself, and so collected the gases which 
were set free. If I were to introduce a certain quantity 
of blood, at the moment when it is drawn from the animal, 
into the vacuum of the barometer, you would observe that 
the column of mercury would fall considerably; and by 
this means also we might collect the gases of the blood. 
Here is a table containing the numbers obtained by Mag- 
nus. 

Table of Gases evolved from the Blood. 

Cubic Centimetres. 

125 parts arterial) ^ 5-4 carbonic acid, 

blood of a horse > 9-8 of gas, compo-ed of < 1-9 oxygen, 

yielded . . 3 f 2*5 azote. 

205 parts venous } C 8-8 carbonic acid, 

blood 



rts venous } C 8-8 carbonic 

of a horse > 12-2 of gas, composed of } 2-3 oxygen. 
3d . . ^ f 11 azote. 

MO- 

of< 4- 

} 1- 



130 parts arterial) C 10-7 carbonic acid, 

blood of a hurse ^ 16-3 of gas, composed of } 4-1 oxyge 
yielded . . > f 1-5 azote. 



LeCT. VI. NATURE OF ARTERIALIZATION. 127 



arts venous i 

d of a horse > 18-9 of gas, composed of 

ied . . S 



170 parts venous ) ^ 12-4 carbonic acid, 

blood 
vielde 




123 parts arterial 
blood of a calf V 14-5 of gas, composed of 
yielded . 

108 parts arterial } 
blood of a calf > 12-6 of gas, compos^ 
yielded . . ^ 

253 parts venous 
b!ood of a calf 
yielded . 

140 parts venous 
blood of a calf 
yielded . 

By taking the mean for these numbers of 100 parts of 
blood, we find that — 

Cubic Centimetres. 

For 100 parts of ^ C 6.4967 carbonic acid, 

arterial blood > 10-4276 of gas, composed of< 2-4178 oxygen, 
yielded ' . j ^1-5131 azote. 



For 100 parts of i C 5-5041 carbonic acid, 

venous blood > 7-6825 of gas, composed of< 1-1703 oxygen, 
yielded . . ) i ^'OOSi ^^ote. 



It is desirable that the experiments of Magnus should 
be repeated and extended, principally in order to ascer- 
tain the absolute quantities of the different gases of the 
blood. 

The following results are also of the highest interest for 
the theory of respiration : — 

1st. There exists in the arterial blood a larger quantity 
of gas than in venous blood. 

2dly. The quantity of oxygen found in arterial blood is 
double that which exists in venous blood. 

Sdly. The ratio between the oxygen and carbonic acid 



128 RESPIRATION. LeCT. VI. 

is from ^ to almost J in arterial blood, which it is only 
from I to even ^ in venous blood. 

Lastly, when we consider the means by which we ex- 
tract the gases from the blood, such as the presence of hy- 
drogen, or a vacuum, it becomes evident that these gases 
are dissolved there. Hence we must admit, that the gases 
thus disengaged from the blood, are set free by the presence 
of other gases, obeying, in this respect, the physical laws 
relating to the interchange which takes place between gases 
dissolved in liquids, and those which are free. 

We have seen that the change cf colour, which venous 
blood undergoes in becoming arterial, — a change effected 
by oxygen, — also takes place when oxygen is separated 
from the blood by a membrane. It is essential, therefore, 
to prove that these phenomena, — that is, the reciprocal ac- 
tion of the gases, and the modification which the colour of 
the blood undergoes, — are effected out of the living body, 
through layers of membranes, and in virtue of laws which 
are altogether physical. 

Any gas placed in a well-closed bladder, soon traverses 
it, and filters rapidly through its pores ; while, at the same 
time, atmospheric air is introduced in its place. If the 
volume of the exterior gas be not infinite, compared to that 
of the gas contained within the bladder, the interchange 
soon ceases, and both outside and inside we shall find an 
uniform mixture of the two gases. Place a bladder, filled 
with water slightly acidulated with carbonic acid, under a 
bell-glass receiver, filled with hydrogen, oxygen, or azote, 
and a portion of carbonic acid will leave the water, and be 
found free in the receiver ; while, at the same time, a por- 
tion of the exterior gas will supply its place, by becoming 
dissolved in the water. In general, two gases, one of which 
is free, or dissolved in a liquid, and the other separated from 
it by a membrane,, mix in definite proportions. 



LeCT. VI. GASEOUS ENDOSMOSE. 129 

Gaseous Endosmose. — It is desirable that an extended 
series of experiments should be carried on, in order to de- 
termine the laws of this phenomenon, having in view the 
reciprocal properties of the gases, their density, and the 
nature of the interposed membranes. Perhaps, a phenome- 
non analogous to that of endosmose may happen between 
the gases. Here is an experiment which shows in what 
way the gases act through membranes, and proves that there 
is a something resembling endosmose in the interchange 
which takes place. I partially filled the lungs of a recently 
killed lamb with oxygen gas, having previously carefully 
extracted, by suction, all the air that it was possible to with- 
draw. The trachea being closely tied, I introduced the 
lungs under a bell-glass, filled with carbonic acid, and in- 
verted under [over ?] water. In a few moments the lungs 
began to swell up, and became as much distended as the 
size of the receiver would admit them to do. I analyzed 
the gas after the experiment, and found that the carbonic 
acid had penetrated into the pulmonary cells, and that the 
oxygen had been disengaged therefrom. The interchange, 
nevertheless, had not been in equal volumes ; the quantity 
of carbonic acid which had been introduced into the lungs, 
being much greater than that of the oxygen which had 
escaped. In a lung prepared in the way I have just men- 
tioned, I found that in four hours, the gas contained in it 
was composed off oxygen, and J carbonic acid, while that 
in the receiver was \ oxygen, and f carbonic acid. 

Soap bubbles, filled with atmospheric air, or hydrogen, 
falling into carbonic acid, demonstrated to Marianini a phe- 
nomenon resembling that which has been observed with the 
lungs. The bubbles augment in size ; and it is curious that, 
when thus dilated, they fall to the bottom of the vessel con- 
taining the acid. The excess of carbonic acid, which has 
penetrated the bubble, is the cause of the augmented 
9 



130 RESPIRATION. LeCT. VI. 

volume. The newly introduced gas produces the increase 
of weight of the whole, and counterbalances the diminution 
arising from the increased volume. But, at the same time, 
the film of water of the bubble certainly dissolves some car- 
bonic acid, and in this way becomes heavier. I have tried 
the effect of placing a carefully closed bladder, having very 
thin sides, and filled with oxygen, in contact v^^ith carbonic 
acid. Taking the precaution that the bladder w^as not moist, 
the distention did not take place ; but after a certain time, 
we found that the interchange between the two gases had 
occurred, though the quantity of carbonic acid which w^as 
introduced, did not exceed that of the oxygen which had 
escaped. Lastly, I filled the lungs entirely with carbonic 
acid, and in this state introduced them into oxygen ; they 
collapsed, and the two gases mixed, but the volume of 
oxygen introduced w'as less than that of the carbonic acid 
which passed out. In all these cases, w^e must also con- 
sider, besides the reciprocal action of the two gases through 
the membrane, the presence of the water, which bathes the 
membranes, — water in which the carbonic acid is soluble. 
The liquid acid thus formed is, on one side, in the presence 
of a gas different to that which it holds in solution, and in 
regard to which the free gas acts as in a vacuum. We 
must, then, take into account the greater quantity of car- 
bonic acid introduced into the soap bubble, or into the lungs, 
by attributing it to a particular action of the two gases, such 
as would constitute gaseous endosmose, and to an effect of 
the gas at first dissolved, then exhaled. In order to clear 
up this question, it is necessary to have recourse to gases 
which have no affinity for water. 

Lastly, we must bear in rnjnd the law^ discovered by 
Graham of the diffusion of gases : the diffusiveness, or dif- 
fusion-volume, of gases separated from each other by a 
membrane, is^ inversely propontiona] to the square roots of 



Lect. VI. 



GASEOUS ENDOSMOSE. 



131 



their density.* According to the recent researches of 
Valentin and Brunner, this law is verified in the pheno- 
menon of respiration. f 

Some facts obtained from experimental physiology, and 
which I have yet to notice, furnish evidence of the strongest 
kind in favour of our conclusions. Spallanzani, Nysten, 
Martigny, and Edwards, removed the air from the lungs of 
some frogs, by making pressure on the breast and abdomen. 
In. this condition, some of the animals were put into hydro- 
gen, and some into azote. Dogs, rabbits, and a great 
number of other animals, were likewise submitted to these 



* In the French edition of Matteucci's lectures, Graham's law is erro- 
neously stated. I have, therefore, corrected the text in the English trans- 
lation. 

Graham's law may be thus expressed mathematically : — 



1 



Diffusiveness = 



Vsp. gT. 

The following Table shows the specific gravities, the square roots of the 
specific gravities, and the diffusiveness of several gaseous substances. 



Gaseous Substances. 


Specific Gravities. 


Square Roots of 
Specific Gravities. 


Dlflfusiveness. 


Air . . . 


1-000 


1-000 


1-000 


Hydrogen . 


0-069 


0.2627 


3-806 


Oxygen 


MU26 


1-05 


0.952 


Nitrogen . 


0-.976 


0-987 


1-013 


Carbonic acid 


1-5241 


1-234 


0-810 


Steam 


0-6202 


0-788 


1-269 








J. P. 



t According to Graham's law of the diffusion of gases, when they are 
separated by an animal membrane and are under equal pressure, they be- 
come mixed inversely as the square roots of their densities ; consequntly 
1-17585 volume of oxygen is absorbed for one volume of expired carbonic 
acid. Comparison of the figures shows us that the mixture of the two 
gases in respiration takes place entirely according to the law of diffusion 
of gases; for a method of experimenting, as accurate as possible, gave re_ 
suits in which the figures obtained for the carbonic acid and absorbed oxy. 



132 



RESPIRATION. 



Lect. VL 



experiments. It was invariably found that the hydrogen or 
azote was absorbed, and in its place carbonic acid and 
azote were exhaled. In pure azote, it was carbonic acid 
only. By introducing, by a syringe, a mixture containing 
more oxygen than exists in atmospheric air, after having 
exhausted the lungs by a syringe, it was observed that the 
exhaled carbonic acid was in greater proportion than that 
which is disengaged by respiring air. Frogs produce car- 
bonic acid in hydrogen and in azote, even w^hen they have 
been deprived of their lungs. 

Conclusion. — From all that has been stated, we cannot 
hesitate to conclude, that the respiratory function is a purely 
physico-chemical phenomenon ; that the gases dissolved in 
venous blood are set free by the absorption of other gases ; 
that a portion of the carbonic acid of venous blood is ex- 
haled by the absorption of atmospheric oxygen by this 
blood ; that it is not in the lungs, at least for the most part, 
that the expired carbonic acid is formed ; that this gas exists 
dissolved in venous blood, and is set free, during the act 
of respiration, by the presence of oxygen, which is intro- 
duced in the same manner as is done by azote or hydrogen 

gen almost exactly agreed with those reckoned according to the law of the 
diffusion of gases : — 



Volume per cent, of 
Carbonic Acid in 
the expired Air. 


Oxygen absorbed. 


Carbonic Acid 
calculated. 


Difference betw e« 
the calculated and 
real quantity of 
Carbonic Acid ex 
pired. 


3-850 
3-593 

3-949 
3-777 
3-759 
4-483 
4-752 
4-588 

1 


4-690 
4.931 
4-487 
4-914 
4-922 
5-698 
6-362 
6-253 


3-994 
4-199 
4-162 
4-192 
4-192 
4-853 
5-418 
5-3:25 


+ 0-144 
+0-606 
+ 0-213 
+ 0-415 
+ 0-433 
4-0.370 
X0 660 
+ 0-737 



Chemical Gazette, vol. ii. 1844, p. 159.— J. P. 



LeCT. VI. GASEOUS ENDOSMOSE. 133 

in the artificial respiration of these gases ; and that, from 
the experiments of Magnus, it is proved, that the quantity 
of carbonic acid dissolved in the five pounds [about 6^ lbs. 
troy] of blood, which traverse the lungs in one minute, is 
nearly double that which is exhaled in the same time. 



134 SANGUIFICATION, LeCT. VII. 



LECTURE VII. 

SANGUIFICATION. — NUTRITION. — ANIMAL HEAT. 

Argument. — HcBmaiosis or Sanguification. Composition of the blood; 
blood corpuscles. Arterialization of the blood ; influence on this pro- 
cess of atmospheric oxygen, — of the removal of carbonic acid, — and 
of the serum ; agency of the iron of the blood. Conversion of arterial 
into venous blood. 

Nutrition ; effected during the passage of the blood through the capillaries ; 
renovation of the tissues; catalytic action of the blood corpuscles. Che- 
mical changes which the blood undergoes in the capillaries. Trans- 
formations of the alkaline salts of the vegetable acids, of benzoic acid, 
and of salicine. Conversion of food into living tissues. Formation of 
urea out of the tissues. Uses of fat. Physiological nature of bile. 

Animal heat. Heat produced in the body by the combustion (oxidation) 
of carbon and hydrogen. Influence of the division of the pneumo- 
gastric nerves. Experiments of Dulong, of Andral, and Gavarret. 
Conclusions. 

Heat evolved by plants during germination and fecundation. 

In the preceding lecture I have shown that, during 
respiration, a portion of the oxygen of the inspired air 
disappears, and that, in its place, is found a volume, 
either equal or less, of carbonic acid ; that the expired air 
is saturated with vapour, and that at the very moment 
when these changes are taking place in the lungs, the ve- 
nous blood is converted into arterial blood. We have also 
seen that all these phenomena occur out of the living 
body and under the same conditions as when they take 
place within it. It now remains for us to examine in de- 



LeCT. VII. COMPOSITION OF THE BLOOD. 135 

tail this modification of the blood. Which of the or- 
ganic elements of the blood undergoes this change ? In 
what does it chemically consist ? If I must reply with 
precision to these questions, I admit that hitherto experi- 
ments made for the purpose of solving them, have thrown 
very little light on the subject, and I can only select, from 
amongst an immense number of experiments, those which 
appear generally to be the least imperfect and the least 
discordant. 

Composition of the Blood. — Micrographers now define 
the blood to be a liquid chiefly composed of water, in 
which are dissolved various salts, albumen, fibrine, and 
fatty bodies ; and in which is suspended a great number of 
red globules, having a definite form, and whose diameter 
is greater or less in different animals. These globules are 
analogous to a vesicle where the coloured involucre is solu- 
ble in acetic acid.* I will show you a beautiful experi- 
ment of Miiller, which will give you a correct idea of the 
composition of the blood. 

I puncture the hearts of a number of living frogs, and 
receive the effluent blood on a paper filter. There flows 
through the paper a yellowish liquid, while the red glo- 
bular matter remains on the filter. In a few moments 
the filtered liquid coagulates and yields a clot composed 
of fibrine. Thus we see, on one side, the colouring mat- 
ter, and on the other, the serum wherein the fibrine was 
dissolved. If the blood had not been filtered, the fibrine 

* The globules, or more correctly the corpuscles, of the blood are be- 
lieved to consist of three parts; — 

1. A capsule^ shell, envelope, or involucre, composed of an albumi- 

nous substance sometimes called globulin. 

2. A nucleus. 

3. An intermediate red colouring matter, apparently in a fluid state 
and called hamatin or hamatosine. — J. P. 



136 SANGUIFICATION. LeCT. VIL 

would have equally coagulated; but in doing so it would 
have enclosed in its mass the suspended globular matter, 
as happens with blood out of the living body. According 
to circumstances which are altogether physical, such as the 
temperature of the blood drawn, the density of the serum, 
and the different proportions of globules and fibrine, co- 
agulation takes place more or less quickly, is more or 
less abundant, and the coagulum formed offers a greater or 
less resistance. 

Mrterialization of the Blood. — If we take the clot formed 
in blood left to itself, and treat it Vv-ith oxygen, we observe 
that it acquires a vermilion colour. This clot, left in the 
air, and then cut, is blackish internally, but red externally. 
The fresh surfaces formed by the incision, soon become red 
by exposure to the air. It is undoubtedly the globules of 
the blood which undergo this change of colour by contact 
with air. 

Baudrimont and Martin Saint-Ange have recently shown 
that at the period of incubation, an absorption of oxygen 
and exhalation of carbonic acid take place through the 
calcareous envelope of the egg; and they have proved, that 
if these phenomena be prevented, the small red globules 
do not appear in the embryo, which does not become de- 
veloped. 

M. Dumas has shown that the globules of the blood 
remain unaffected, and without dissolving, if we carefully 
expose them to the contact of atmospheric air continually 
renewed. 

It yet remains to be ascertained whether these globules 
become red solely by the oxygen which they absorb, or by 
the loss of carbonic acid which they suffer during respira- 
tion ; or if, on the contrary, the blood becomes venous in 
consequence of the larger quantity of carbonic acid with 
which it is charged, or on account of the smaller quantity 



LeCT. VII. AGENCY OF IRON. 1 37 

of oxygen which remains with it, or if it be the effect of 
these two circumstances combined. To explain this matter 
clearly accurate experiments are wanting. 

Magnus has proved that venous blood, in losing the 
greatest possible quantity of carbonic acid, becomes less 
deeply coloured, but without ever acquiring a vermilion tint. 
This fact leads us to assume that these two causes have a 
simultaneous influence on the change of colour which the 
blood undergoes during respiration. 

I ought to add, that if we carefully remove all the serum 
which surrounds the coagulum, and afterwards wash the 
latter with distilled water to deprive it of every trace of 
serum, it in this state no longer acquires, by contact with 
oxygen, that beautiful vermilion colour which it assumes 
when it is immersed in the serum. Here is a saturated 
solution of common salt, which I pour, drop by drop, on 
the blood clot; and you perceive that those parts on which 
the drops fall, acquire a vermilion colour, whilst the other 
parts of the surface undergo no change. 

It appears, then, that the salts of the serum are not pas- 
sive in the modification which the colour of the blood under- 
goes in the presence of oxygen. We now know that the 
serum absorbs a much greater quantity of carbonic acid 
than can be dissolved by water. We may, therefore, say 
that the serum influences the change of colour of the blood, 
in consequence of containing a portion of carbonic acid, of 
which it is afterwards deprived by the oxygen. 

Agency of Iron. — But how can we account chemically for 
the change in the colour of the blood globules? On this 
point science has not hitherto enhghtened us. The large 
quantity of iron (5 or 6 for 100) which invariably exists in 
these globules, and is met with, in this proportion, in no 
other animal substance, has given rise to the idea that this 
metal, found in the blood, sometimes in the condition of 



138 SANGUIFICATION. LeCT. VII. 

peroxide, and sometimes as a carbonate [of the protoxide,] 
must hav^e some influence in effecting the change of colour. 
In fact, oxygen, expels carbonic acid from carbonate of 
iron, while carbonic acid replaces the oxygen of the peroxide, 
according to the relative proportions of oxygen and carbonic 
acid present. 

Mulder and Liebig appear to have adopted these opinions. 
All the best established clinical results apparently prove that 
the use of iron in certain maladies restores in some way the 
colour of the blood. Nevertheless, Scherer has recently 
satisfied himself that he obtained the colouring matter of 
the blood entirely free from iron. If Scherer's observation 
be ultimately confirmed, and if, moreover, it be proved that 
this colouring matter, deprived of iron, undergoes, by con- 
tact with oxygen and carbonic acid, the changes which we 
have seen take place in the blood globules, we shall be 
compelled to give up the idea that iron intervenes in thQ 
change of the colour of the blood. 

Conversion of arterial into venous Blood. — The arterial 
blood, propelled by incessantly renewed contractions of the 
heart, as well as by the successive dilations and contractions 
of the coats of the arterial vessels, owing to their peculiar 
elasticity, arrives with this red colour in the last capillary 
ramifications. Still contained in these vessels, it traverses 
all the tissues, loses its red colour, and returns by the veins 
to the heart in order to pass again into the lungs. 

Renovation of the Tissues. — Physiologists tells us that 
nutrition takes place during the passage of the arterial blood 
through the capillaries. They assume that every portion 
of the animal tissues is incessantly renewed and transform- 
ed ; and that these phenomena vary in intensity, and are 
proportionate to the different degrees of activity of the 
capillary systems of the different tissues. In truth, experi- 
mental evidence of this renovation is still wanting; and that 



LeCT VII. CATALYTIC ACTION. 139 

which consists in the colouration of the osseous parts of 
animals fed with colouring substances, and then in their 
decolorization when such nutrition is stopped, has always 
appeared to me insufficient. It must, however, be admitted 
that physiological facts, generally support the idea of this 
renovation. 

If I were here to mention to you the various kinds of 
experimental information still wanting, and which are 
necessary to elucidate the function of nutrition, I should 
occupy much more of your time than if I undertook to de- 
scribe all that we really know on this subject. 

Catalytic Action of the Blood Globules.^ — The blood glo- 
bules, making no part of the tissue, though being essential 
to nutrition, may, with a certain amount of probability, be 
regarded as the catalytic body which promotes the trans- 
formation and continual yenovation of the tissues. An 
analogy of this characteristic of the globules is to be found 
in the necessity which they experience of being charged 
with oxygen in order to acquire this property. 

Observe also that as in vegetables, diastase converts 
starch into dextrine, which is afterwards formed into cellu- 
lose and wood, that is to say, into bodies which are iso- 
meric with each other, so [in animals] the blood globules 
change albumen into fibrine, — a transformation which cer- 
tainly occurs in the embryo. 

I wish I were able to say that the reality of these changes 
had been demonstrated as in the case of starch. I have 
made a great many experiments, having this object in 
view ; but the results which I have hitherto obtained still 
leave me in doubt. I kept for a month at the constant 
temperature of + 40° centig. [= 104° Fahr.,] the albu- 
men of the egg mixed with a small quantity of the blood 
globules of a fowl in the presence of oxygen. A receiver 
used for collecting water offered me the convenience of a 



140 SANGUIFICATION. LeCT. VII. 

medium constantly at the same degree of heat. I saw that 
oxygen in part disappeared, that it was replaced by carbonic 
acid, and that at the bottom of the receiver was deposited 
a great number of reddish flocculi; yet the primitive liquid 
was limpid and scarcely coloured. These flocculi on exa- 
mination did not appear to me to be identical with fibrine. 
Nevertheless, I do not wish to conclude from these negative 
results that the principle, on which my experiments were 
founded, was false. It is a subject which claims very long 
and very varied researches. 

Changes in the Blood of the Capillaries. — Let us return 
to our first subject. In the act of nutrition, a part of the 
oxygen of the arterial blood disappears, and is replaced by 
an excess of carbonic acid in the venous blood. In the 
capillary vessels, oxygen combines with carbon ; it is cer- 
tainly here that this combination takes place ; and since we 
find that the volume of carbonic acid expired is smaller than 
that of the oxygen which has disappeared in respiration, we 
must admit that not only the carbon, but even the hydro- 
gen, which made part of the organic elements of the blood 
and the tissues, combines with the oxygen to form water. 
Here, then, is another instance of combustion besides that 
of carbon. 

The acetates, the tartrates, and the oxalates, which enter 
in a state of solution into the blood, escape by the urinary 
passages in the form of carbonates. Benzoic acid intro- 
duced into the circulation escapes in the condition of hip- 
puric acid also through these passages. I may also men- 
tion that, in conjunction with Professor Piria, I introduced 
into the circulating blood of a living animal a solution of 
salicine. After some time we discovered in the urine a 
substance derived from salicine, and which had the pro- 
perty of forming a violet precipitate on the addition of a 
salt of iron. 



LeCT. VII. COMBUSTION DURING CIRCULATION. 141 

An important observation recently made by Dessians de- 
serves to be noticed here. By boiling hippuric acid with a 
solution of hydrochloric acid, benzoic acid was precipi- 
tated and hydrochloric acid obtained in solution, combined 
with a saccharine azotised matter, which was found to be 
Braconnot's gelatine-sugar. We know that this substance 
(gelatine-sugar) is obtained by treating neutral azotised 
matters (proteine and gelatine) with acids. We further 
know that hippuric acid replaces, in the herbivora, the se- 
cretion of urea in the carnivora. We may infer from this, 
that gelatine-sugar is one of the first products of the trans- 
formation of neutral azotised matters, which are the mate- 
rials of the tissues. We may thus comprehend how, by 
adding benzoic acid, which combines with them, hippuric 
acid may be obtained. 

Combustion during Circulation. — All these facts prove 
beyond doubt that the principal chemical action observed 
in the circulation of the blood, and in nutrition, is a com- 
bustion, that is, a combination of oxygen with the carbon 
and hydrogen of the organic tissues. But, I repeat, up to 
the present time, great obscurity prevails in our knowledge 
of the series of these phenomena. What difference exists 
between the chemical composition of all the elements of the 
arterial blood, and that of all the elements of the venous 
blood ?* What is the nature of this difference in the blood 

* According to Dr. G. O. Rees {Proceedings of the Royal Society, for 
June 3d, 1847,) venous blood contains a phosphoric fat, and arterial blood, 
a tribasic phosphate of soda. " The venous corpuscles are known to con- 
tain fat in combination with phosphorus. This compound ingredient of 
the corpuscles, on coming into contact with atmospheric oxygen during 
the respiratory act, is consumed, and combining with that oxygen, forms 
the carbonic acid and water which are expired ; and also phosphoric acid, 
which, uniting with the alkali of the liquor sanguinis, forms a tribasic 
phosphate of soda. This salt, like many others, acts upon htematosine in 
such a manner as to produce the well-known bright arterial tint," — J. P. 



142 SANGUIFICATION. LeCT. VII. 

before and after its passage through the kidneys, the liver, 
and the various tissues ? These are among the numerous 
questions which should be resolved by very accurate expe- 
riments, and by researches agreeing in their results, before 
prosecuting our investigations on the phenomena of nutri- 
tion and secretion. 

Source of Evolved Products. — As we have seen, the ali- 
ments pass into the blood after having undergone various 
modifications by the act of digestion. Among these, many 
are identical with the organic elements of the animal tis- 
sues : this is the case with the neutral azotised substances. 
So, also, with the fatty matters of the aliments, which are 
found in the adipose tissues scarcely, if at all, altered. It 
would be both unreasonable and absurd to assume that the 
urea, carbonic acid, and water, which are the definite pro- 
ducts of transformations going on during nutrition, are de- 
rived from those organic elements of the blood, which were 
introduced by the aliments. We must suppose that these 
products are the results of transformations which the mate- 
rials of our tissues have undergone, and which are replaced 
by new organic elements supplied by the food. And, in 
fact, the production of urea takes place in animals nou- 
rished for a long time with sugar, starch, and gum, just as 
it had done before this kind of food was used. The same 
thing is observed in animals that have died from inanition. 

For the sake of accuracy I shall quote, on the subject of 
these transformations, some illustrations taken from Liebig's 
^^ Animal Chemistry^ or Organic Chemistry in its Applica- 
tions to Physiology and Pathology ^ 

A serpent, kept for some time without food, and then fed 
on a goat, a rabbit, or a bird, expelled from the body, ap- 
parently unchanged, the hair, hoofs, horns, feathers, or 
bones of the devoured animal ; exhaled carbonic acid and 
water ; and evacuated by the urinary passages urate of am- 
mo aia. 



LeCT. VII. SOURCE OF THE CARBON EVOLVED. 143 

When the serpent had regained its original weight no 
trace of its prey was discoverable. Let us analyze this 
simple case of nutrition. The urate of ammonia contains 1 
equivalent of azote for 2 equivalents of carbon ; the muscles 
and the blood of the animal eaten contain 8 equivalents of 
carbon for 1 of azote ; and if we add to this the carbon con- 
tained in the fat and nervous substance, it is obvious that 
the serpent took more than 8 equivalents of carbon for 
every equivalent of azote. Now in the excrements only 2 
equivalents of carbon were found ; the 6 equivalents missing, 
must have been given out in the form of carbonic acid. I 
shall not stop to repeat to you our belief that the urate of 
ammonia and carbonic acid are derived from the trans- 
formed animal tissues, the place of which has been supplied 
by equivalents taken from the organic elements of the di- 
gested animal. We always find as much carbon and azote 
in the products of the transformation which the tissues 
suffer, in the presence of arterial blood, as the tissues them- 
selves derive from the blood or the aliments. 

What t have now told you of the serpent, holds good 
with the lion and all carnivora: in their urine there is urea 
only, which contains an equal number of equivalents of 
azote and carbon. As these animals are nourished on 
meat which contains azote and carbon in the ratio of 8 
equivalents to 1, it follows that all the introduced carbon, 
beyond the amount which we find in the urine, must have 
disappeared in the process of respiration, have been burnt 
and converted into carbonic acid. The respiration of the 
lion is certainly much more active than that of the serpent. 

The fifteen or twenty grammes [about 231J grs. to about 
309 grs. troy] of azote which a man daily passes in his 
urine, as well as the excess of azote which he expires, 
comes from the neutral azotised substances with which he 
is nourished, and more directly from the transformed tissues 
which the alimentary substances are about to replace. 



144 SANGUIFICATION. LeCT. VII. 

Boussingault has proved by experiment that, in the urine 
of the horse, is found all the azote which formed part of its 
food; and he has thereby demonstrated, that the excess of 
azote expired equally proceeds from the aliments. 

It is impossible, in the present state of science, to say 
precisely through what series of modifications and inter- 
mediate products, the muscles, cartilages, &c., pass, in 
order to be converted into urea under the action of the 
oxygen of the blood globules. By adding to the formula 
of proteine, which at the same time is also the formula of 
albumen, caseine and fibrine, as much oxygen as is neces- 
sary to convert it into urea, and to convert the excess of 
hydrogen and carbon into water and carbonic acid, we 
obtain quantities of carbonic acid and water which are 
much smaller than those produced by respiration. Here 
is a numerical example deduced from the experiments of 
Boussingault, which I give you the better to establish 
the fact, that the carbon of azotised foods converted 
into urea, is much less than that which animals produce 
in the form of carbonic acid. The following are the 
numbers: a horse was kept in a perfect state of health, by 
eating daily 7J- kilogrammes of hay and 2^ kilogrammes of 
oats. Analytical researches show that the azote of the hay 
is 1'5, and that of the oats 2*2 per cent. If we assume 
that all the azote of the aliments is reduced in the blood to 
the condition of fibrine and albumen, there would then be 
140 grammes of azote introduced into the blood, and 
destined to replace the azote which goes out in the pro- 
ducts of the transformed tissues. The quantity of carbon 
taken simultaneously with the azote [in the fibrine and albu- 
men] amounts to 480 grammes; and of those only a portion 
can be converted into carbonic acid during respiration, 
since the horse converts part of the carbon into urea, and 
a portion into hippuric acid. But a horse, according to 
the experiments of this chemist, evolves by respiration in 



LeCT. VII. ELEMENTS OF RESPIRATION. 145 

the space of one day, 2465 grammes of carbon in the state 
of carbonic acid. It is very clear, then, that the carbon of 
the azotised principles of the aliments is only a small por- 
tion of that which is found in the carbonic acid expired. 

JVecessity for the Elements of Respiration. — Hence arises 
the necessity of other kinds of foods, to supply the deficiency 
of carbon of the azotised aliments. Starch, gum, or sugar, 
and the fatty bodies, come under this category. In all 
cases where the animal economy is destined to grow, as in 
the young animal, nature has augmented, in its foods, the 
proportion of those ingredients which furnish the carbon 
and hydrogen lost by respiration ; and in this way the azo- 
tised aliments, destined for the growth of the tissues, are 
economised. 

By successively ascertaining the weight of the fatty mat- 
ters, and the azotised neutral matters in the egg of the 
chick, during the period of incubation, and in the chick 
itself after its escape from the egg^ Dr. Cappenzuoli has re- 
cently discovered, that about the seventeenth day, that is 
to say, a short time before the chick is hatched, there is a 
sensible diminution of the fatty and azotised neutral matters, 
and that this diminution gradually augments. 

With respect to the fatty bodies, it seems that these are 
exclusively employed in respiration, in those cases only 
where the starch, sugar, and gum are insufficient. Hence, 
the fat disappears in hybernating animals, and in those 
which remain a long time without food. These bodies 
appear to be, physiologically, destined for the formation of 
the cerebral and nervous substance, and to fill the interstices 
of the cellular tissue, where are kept in store the materials 
for respiration.* 

* Fatty matter appears also to be intimately concerned in growth and 
nutrition, healthy and diseased. See some interesting remarks on this 
subject by Mr. Gulliver, in The WorJcB of Hewson^ p. 88, published by the 
Sydenham Society. — J. P. 

10 



146 SANGUIFICATION. LeCT. VII. 

Use of the Bile. — I must also notice Liebig's hypotheti- 
cal views respecting the liver. Physiologists no longer 
regard the bile as an excretion only. This becomes obvi- 
ous, when we remember that Berzelius found only 9 parts 
of a matter resembling bile in IQOO parts of human excre- 
ments ; that is to say, a man who secretes in one day from 
500 to 700 grammes if bile, will reject with his excrements 
only JO or tV part only. Moreover, it cannot be supposed, 
that a matter so slightly azotised as bile is, can be useful 
in nutrition. Lastly, we have seen that bile performs little 
or no part in digestion. Liebig assumes, that the bile 
poured into the duodenum forms a soluble combination 
with potash which is absorbed and converted into carbonate 
of potash by yielding up a portion of its carbon to the 
oxygen. In confirmation of these views, experiments are 
still wanting ; and the more so, as it is only in some pa- 
thological cases, and under certain atmospherical condi- 
tions, that traces of biliary matter have been discovered in 
the blood. 

Whether these hypothetical notions respecting nutrition, 
be or be not well founded, one thing is certain, namely, 
that an adult man absorbs in one day about 1015 grammes of 
oxygen. The observations of Dumas, Andrat, Gavarret, 
and the still more recent ones of Scharling, show that, on 
an everage, a man exhales in a day 224 grammes of car- 
bon, in the form of carbonic acid ; that men exhale more 
than women, and children more than men ; and that more 
is exhaled in the waking state than in sleep. A horse 
gives out, in the form of carbonic acid, 2465 grammes of 
carbon, consuming, for this, 6504 grammes of oxygen. A 
milch cow exhales 2212 grammes of carbon, in the form 
of carbonic acid, for which 5833 grammes of oxygen have 
been consumed. The quantities of food, then, are neces- 
sarily proportionate to the quantity of oxygen respired, and 



Lect. VII. animal heat. 147 

of carbonic acid exhaled. The activity of the respiratory- 
movements, the density of the respired air, and the quan- 
tity of carbon introduced in the aliments, ought to be in 
proportion to each other, in order to preserve the materials 
of the animal economy. Letellier has lately proved that, 
with birds and guinea-pigs, the quantity of oxygen con- 
sumed in respiration is smaller, in proportion as the 
temperature of the air is higher. The carbonic acid ex- 
haled at 0° centig. [= 32° Fahr.] he found to be double 
that produced at the temperature of + 15° to 20° centig. 
[= 59° Fahr. to 68°.] 

In those animals in which the activity of the respiratory 
raovements'is greater, the capillary circulation more rapid, 
and the quantity of the blood-globules more considerable, 
the portion of the fat in their tissues is very small. This 
is the case with birds, the hyena, and the tiger. If these 
animals be allowed but little or no exercise, fat soon ac- 
cumulates in their tissues. From the experiments of Tre- 
viramus, we learn that, if their weights be equal, a cold- 
blooded animal consumes ten times less oxygen than a 
mammal, and nineteen times less than a bird. 

Finally, I think it important to notice the results of a 
great number of experiments made by Boussingault, to de- 
termine, by a comparison of the composition of the aliments 
with that of the excrements, whether any azote be exhaled 
during respiration by graminivorous animals. 

By taking the mean of his results, we find that a turtle- 
dove consumes, in 24 hours, 5*10 grammes of carbon, and 
in the same space of time gives out 18-70 grammes of 
carbonic acid {i. e. 565*165 cubic inches,) and 0-16 gram- 
mes of .azote (i e. 7*69 cubic inches.) The azote, there- 
fore, is jh part of the volume of carbonic acid, a propor- 
tion below that found by Dulong and Despretz. The 
hydrogen consumed in one day is 0*07 gramme ; so that 



148 SANGUIFICATION. LeCT. VH. 

from these results we learn that a turtle-dove weighing 
187 grammes, and respiring freely at the temperature of 
+ 8° to 10° centig. [= 46-5 Fahr. to 50°] can, by con- 
suming in 24 hours 5-1 grammes of carbon, and 0-07 
grammes of hydrogen, develop all the heat required to 
maintain the body at the temperature of + 41° to 42° 
centig. [= l05°-8 Fahr. to 107°-6,] and at the same time 
exhale about 3 grammes of aqueous vapour from the lungs 
and skin. 

Animal Heat. — It is, then, indisputable that an animal 
is an actual apparatus of combustion, in which carbon is 
constantly burnt, and from which carbonic acid is always 
escaping. Such a calorific apparatus has been so consti- 
tuted as to have, in comparison with the temperature of the 
surrounding air, a constant, or but a shghtly variable, ex- 
cess of caloric. This excess varies, according to the 
rapidity of the combustion in this animal calorific appara- 
tus, and according to the constant temperature of the sur- 
rounding medium in which it lives. 1 gramme of iron, 
which oxydizes in the air, and 1 gramme of iron, which 
oxydizes in oxygen gas, develop each the same amount of 
heat ; but the latter oxydizes in a second, perhaps, whilst 
the other takes several hours to perform the same process. 
Hence, the temperature possessed by the one is vastly greater 
than that of the other. A mass of grape husks, laid in a 
heap, undergoes fermentations and becomes very hot ; but 
the same quantity, arranged in a thin layer, evolves an 
equal amount of heat, but which is not perceptible, in con- 
sequence of being too much dispersed. In this way, we 
can understand the difference of temperature between warm 
and cold-blooded animals. We cannot have arty doubt as 
to the source of animal heat. It is found in the chemical 
re-actions of respiration effected in the capillaries, in the 



LeCT. VII. ANIMAL HEAT. 149 

transformation of tissues, and especially in the combination 
of oxygen with carbon.* 

I have no wish, nor, indeed, am I able, to describe any 
other hypothesis relating to the sources of animal heat. 
When, in consequence of dividing the pneumo-gastric 
nerves, or the spinal marrow, we find, by a thermometer 
placed in the tissues of the animal, that the temperature 
falls, and from this conclude that innervation was the direct 
cause of animal heat, we do not consider that respiration 
and the circulation of the blood have been diminished in 
consequence of the division of the nerves and spinal cord. 
Instead of discussing hypotheses like these, it is preferable 
to examine more deeply, and in detail, the chemical ac- 
tions which we consider to be the sole source of animal 
heat. 

Natural philosophers are anxious to prove the truth of 
these hypotheses. An animal exhales, in a given time, a 
certain quantity of carbonic acid and water, and simultane- 
ously developes a quantity of heat, which may be measured 
by the quantity of water which it is capable of heating in 
the same space of time. If the carbonic acid and the 
water, which the animal exhales, be the products of the 
combustion of carbon and of hydrogen, the heat given out 
by the animal ought, these philosophers say, to be equal to 
that which the same quantities of carbon and hydrogen 
produce when burnt in the air. 

By setting out with the data furnished by a calorimeter, 
in which the animal was placed*, noting the temperature 
acquired by the water, and measuring, at the same time, 
the oxygen which the animal or its products, carbonic acid 

* If Dr. G. O. Rees's theory of respiration be correct (see foot-note at 
p. 141,) the oxidation of phosphorus, contained in the venous corpuscles, 
must be one source of animal heat. — J. P. 



150 SANGUIFICATION. LecT. VIL 

and water, absorbed, Dulong, and afterwards Despretz, 
found that for every 100 parts of heat produced by the 
animal, and received by the calorimeter, 80 or 90 only 
were produced by the combustion of the carbon and hy- 
drogen,- — calculating from the carbonic acid and water 
evolved by the animal. 

If we reflect that the temperature of an animal placed in 
a calorimeter, is always higher than that of the surrounding 
water, and that the animal is in consequence cooled during 
the experiment, we find, in the fact of this refrigeration, a 
plausible explanation of the excess of caloric met with. 
And, indeed, the numerous experiments of Despretz have 
clearly proved that the excess of heat received by a calori- 
meter over that which is due to respiratory combustion, is 
greater in proportion as the animal is younger and its tem- 
perature higher. We know, moreover, from the beautiful 
experiments of Edwards, that young animals cool much 
more rapidly than adults. 

These considerations are suflScient to show that the excess 
met with in the calorimeter can be explained, without 
having recourse to any special power, to a vital property 
which engenders heat. 

I must also add, that after the death of the celebrate^ 
Dulong, there was found in his unpublished papers an 
account of several other experiments relating to the heat 
developed by the combustion of hydrogen. This heat 
should be much more considerable than that which was 
first found by Dulong and Despretz. The numbers fixed 
by the later experiments of Dulong have since been con- 
firmed by those of Fabre and Silberman. Now, in adopt- 
ing this new number, we no longer find an excess of heat 
yielded to the calorimeter over that developed by the com- 
bustion of hydrogen and carbon, but on the contrary, a 
deficiency. 



LeCT. VII. ANIMAL HEAT. 151 

We have, therefore, no occasion to seek for other sources 
of animal heat than the chemical processes of respiration 
and nutrition ; but I think it is an error to attempt to make 
a rigorous comparison of the results of experiments on ordi- 
nary combustion produced in a calorimeter, with those 
which happen in an animal ; and to admit, as the source of 
animal heat, one only of the numerous chemical actions 
which take place within the same animal. 

In fact, the carbonic acid with which the venous blood 
is charged, and which is produced by the union of atmos- 
pheric oxygen with the carbon of the organic elements of 
the different tissues which become modified, cannot arise 
from the carbon existing in a free state in these tissues, but 
in combinations with which we are far from being perfectly 
acquainted. 

The experiments of Dulong prove that one body com- 
bined with another does not produce, in burning, or in 
combining with oxygen, the same amount of heat which it 
would do if it were employed in its free state. The heat 
which bicarburetted hydrogen, marsh gas, and oil of turpen- 
tine, produce, by burning in oxygen, and forming water 
and carbonic acid, is not equal to, but is generally less than, 
the amount of heat which would have been furnished, had 
the volumes of gas composing them been burnt separately. 
The experiments of Hess and Andrews, which tend to prove 
that in a given combination, an absolute quantity of heat is 
developed, whatever may be the condition of the two com- 
bining bodies, have related solely to the successive com- 
binations of the same body, as in the case of sulphuric acid, 
which combines with different numbers of atoms of water. 

If we must limit the explanation of the production of 
animal heat, exclusively to the chemical combination of 
carbon and of hydrogen with oxygen, it will be difficult to 
interpret the results which have been arrived at by Andral 



152 SANGUIFICATION. LeCT. VII. 

and Gavarret in their study of the exhalation of carbonic 
acid during the act of respiration in man. 

From the very extensive and apparently accurate experi- 
ments of these distinguished physiologists, it appears that 
carbonic acid which is exhaled during respiration varies 
much according to the sex, the age, and some particular 
physiological conditions. The difference between the 
numbers 5 and 14*4, expressing with the latter the quan- 
tities, taken in grammes, of carbon, which contribute to 
form the carbonic acid expired during an hour. The first 
of these numbers was obtained in a child of eight years old, 
and the other in a young man of twenly-six years of age. 
Observe, however, that in children the temperature being 
considerably higher than in adults, and the mass which is 
heated in these latter being larger, the loss of heat which 
they suffer ought to be proportionately greater. 

Andral and Gavarret have also found, that in females the 
establishment of puberty does not augment the quantity of 
carbonic acid exhaled, but that this exhalation becomes 
more active when age or other causes put a stop to the 
phenomenon of menstruation. 

Notwithstanding this, we remark no perceptible difference 
of temperature in the body of a female before, after, or during 
the period of menstruation, or in the state of pregnancy. 
And without having recourse to these experimental data, it 
will be sufficient to consider that in certain maladies there 
is a rapid diminution of temperature, and in others, on the 
contrary, a very great increase throughout the body, without 
our being able to admit of a corresponding variation in the 
respiratory function. 

Conclusions, --^Let us conclude, then, that in the exist- 
ing state of physico-chemical knowledge, it must be assumed 
that the chemical actions which take place in animals during 
the transformation of their tissues, under the influence of 



LeCT. VII. HEAT OF VEGETABLES. 153 

atmospheric oxygen, are the source of heat in them ; that 
among these, combustion of carbon and of hydrogen ought 
to be considered as one of the principal, but not the only 
one ; and that experimental data are yet wanting to discover 
the exact ratio between the heat produced by an animal, and 
the heat evolved by chemical actions going on within it, 
and by those which we are able to produce with our appa- 
ratus. 

Heat of Vegetables. — I shall not leave this subject without 
telling you, that in vegetables, also, the heat developed by 
germination is a phenomenon of chemical action, due to the 
combination of oxygen with the carbon of the germinating 
seed. We know that in the process of germination, there 
is an absorption of oxygen, and the evolution of carbonic 
acid, and that diastase converts starch into dextrine and 
sugar, which afterwards disappears by producing carbonic 
acid. It is curious, that in plants, as in animals, there are 
starch and sugar, which, by burning, disengage the heat 
necessary to |heir existence. In a like manner must be ex- 
plained the heat which accompanies the fecundation of 
plants. Hence, we find, that in the sugar-cane, the beet- 
root, and the carrot, the sugar disappears after the flowering 
and fructification. 



154 PHOSPHORESCENCE. LeCT. VIII. 



LECTURE VIII. 

PHOSPHORESCENCE OF ORGANIZED BEINGS. 

Argument.— General remarks. 

Phosphorescence of the Glowworm ; effects of heat and cold on it ; in- 
fluence of carbonic acid, of hydrogen, of atmospheric air, of chlorine, 
of oxygen, of mixed gases, of sulphuretted hydrogen, and of rarefied 
air. General conclusions. Cause of the phosphorescence : is not de- 
pendent on insolation ; agency of the nervous system ; influence of 
poisons. Microscopic structure of the luminous organs. Chemical 
nature of the phosphorescent substance. Conclusions as to the cause 
of the phosphorescence. 

Phosphorescence of animalcules; of putrescent ^sh ; of the human body ; 
of the perspiration ; of the anndides and ophiurcz ; of plants. 

Phosphorescence of Living Beings. — Living beings do 
not produce heat merely, many of them give out light also. 
Although the latter be not a general phenomenon proper to 
all organized beings, yet the numerous cases of it known 
are of the highest importance, and they show us a singular 
faculty of the living organism. We shall see in this lec- 
ture, in studying the best known cases of animal phospho- 
rescence, that the phenomenon involves physico-chemical 
theories, so far as the general m^de of its production is 
concerned; and that its exceptional character is one of 
thoge mysterious singularities which nature seems to have 
distributed amidst the immense variety of beings, almost 
without any previous attention to the animals on which she 
bestows them, as if merely for the purpose of constraining 
us to admire with humility the power of her creative skill. 



LeCT. VIII. GLOW-WORM. 155 

Glow-worm. — I shall engage your attention for some 
time on the phosphorescence of a well-known insect, by 
giving you an account of the most conclusiv.e experiments 
made some time since by Macaire and other natural philoso- 
phers, and recently by myself. The insect I speak of, is 
the Lampyris Italica* or Italian glow-worm, commonly 
called ver luisant in France, and lucciola in Italy. It is a 
coleopterous insect living in the grass, and which shows it- 
self after sunset in spring and summer. The two last seg- 
ments of its body, which by day appear yellowish, are slightly 
luminous in the dusk, and during the night evolve a bright 
intermittent light. 

The light sometimes ceases suddenly, either when the 
insects are gently touched, or at times when they have not 
been touched, and subsequently re-appears again. 

This fact led Macaire to suppose, that the phosphores- 
cence was under the will of the animal. The cessation of 
the luminosity is certainly not effected by an opaque mem- 
brane, which it was supposed the insect drew over its rings, 
for no such membrane exists. 

We shall find, in the course of this lecture, that every- 
thing leads us to assume that the phosphorescence is not 
continuous, because the cause that produces it is not persis- 
tent ; and that we can explain the intermittence of the phe- 
nomenon. 

In studying this subject, the observation which has always 
excited my astonishment is, that the yellowish matter con- 
tained in the terminal rings of the insect continues to emit 
light when separated from the body of the animal. If we 
kill one of the insects and crush it between the fingers, 
long streaks of light are perceived to issue from the yellow- 

* The insect above noticed, under the name of Lampyris Italica, is by 
some authors referred to another genus. In Dejean's Catalogue it is 
called, Colophotia Italica. — J. P. 



156 PHOSPHORESCENCE. LeCT. VIII. 

ish matter. The phosphorescence continues for a greater 
or less period, according to a variety of circumstances, 
which we shall presently investigate. Indeed, this fact 
proves that the integrity and life of the animal are not es- 
sentially necessary for its production. In order to study 
the matter, thus separated from the body of the insect, I 
commenced by examining what influence heat, electricity, 
and gaseous media had on it, as those persons had done, 
who preceded me in this curious inquiry. At the same 
time, I also studied the influence of the same causes on an 
entire and living insect ; and thus, by comparison, I believe 
I have adopted the best method of ascertaining the nature 
of the phenomenon. 

Effect of Heat on the Glow-worm. — I placed several very 
lively and very luminous glow-worms in a glass tube im- 
mersed in water. A thermometer with a very small bulb 
was surrounded by these insects. I have repeatedly endea- 
voured to ascertain whether the thermometer thus placed 
acquired, in consequence, a higher temperature, but have 
never observed that it did. By slowly heating the water, I 
saw the intensity of the light increase up to -f 30° Reau- 
mur. [ = 99-5° Fahr.] At about this temperature the in- 
termittence ceased, the light became continuous, and, by 
applying more heat, acquired a red colour. At + 40° 
Reaumur [ = 122° Fahr.] the light entirely and finally 
ceased, and the animal died. By crushing the matter from 
the rings between the fingers, it no longer evolved light. 

In experimenting with the posterior luminous segments, 
instead of entire glow-worms, I discovered no difference 
in the phenomena. These results confirm the experiments 
made by Macaire on entire glow-worms, placed in water 
which was gradually heated. 

Effect of Cold. — I found some differences between my 
results and those obtained by this philosopher when the 



LeCT. VIII. EFFECT OF CARBONIC ACID. 157 

insects were submitted, in the same way, to the influence 
of cold. The tube being placed in ice, the light had not 
ceased even at the end of fifteen or twenty minutes, though 
it was more feeble, and not intermitting. When with- 
drawn from the tube and placed on the hand, the animals 
became as brilliant as ever. The same effect was obtained 
with the posterior luminous segments. The tube contain- 
ing the glow-worms and thermometer being placed in a 
freezing mixture, whose temperature was 5° Reaumur [ — 
20*75° Fahr.] the animals ceased to shine, and appeared 
motionless in about eight or ten minutes ; but when they 
were withdrawn and placed on the hand, life returned, and 
with it hght. If, during the time they are in the tube at 
5° Reaumur [ = 20*75° Fahr.] their segments be broken 
by a pointed wire, a transient and very feeble light appears. 
This fact is likewise confirmed by the observation that their 
isolated posterior segments or luminous matter cease to 
shine at this temperature. If the luminous matter thus 
cooled be withdrawn and re-warmed, it recovers its billian- 
cy for an instant, and the light before becoming extinct 
acquires, as usual, a red colour when the heat has been too 
strong. 

Effect of Carbonic Acid. — I put, at the same time, into 
two small equal-sized bell glasses ten glow-worms, and an 
equal number of segments detached from other similar in- 
sects. Then, after having filled the two glasses with mer- 
cury, I introduced some carbonic acid. In a few minutes, 
the light entirely disappeared, but without any remarkable 
difference being observed between the segments and the 
entire insects. When I introduced a little air, all reco- 
vered their luminosity ; and, by adding some bubbles of 
oxygen, the effect took place more rapidly and brilliantly. 
Glow-worms, which appeared dead in carbonic acid, re- 
turned to life and motion on the introduction of oxygen. 



158 PHOSPHORESCENCE. LeCT. VIII. 

If thirty or forty minutes intervened, before the introduc- 
tion of the air or oxygen, the insects neither returned to 
life nor re-acquired their phosphorescent quality ; the seg- 
ments alone, having remained much longer in the carbonic 
acid without being luminous, re-acquired their phosphores- 
cence when oxygen w^as introduced. 

Effect of Hydrogen. — When we used hydrogen, in place 
of carbonic acid, the insects, as well as their separated lu- 
minous parts, preserved their phosphorescence only for a 
time, which was somewhat longer than that stated for car- 
bonic acid. The diiference was scarcely perceptible with 
entire insects ; but was more considerable with the de- 
tached luminous segments. In one instance, I saw the 
phophorescence continue in hydrogen for twenty- five or 
thirty minutes. And even insects that did not glow, in 
hydrogen, returned to life and instantly re-acquired their 
phosphorescence when they were exposed to the air, or, 
better still, to oxygen gas ; provided that not more than 
five or ten minutes had elapsed after the cessation of the 
light. 

I invariably observed that, with the entire insects, the 
intermittance cea*sed before the light had altogether disap- 
peared. 

Some hours after the glow-worms, or their luminous 
segments, had ceased to shine, a feeble but very visible 
light was obtained by crushing them on the hand, but it 
was only momentary. 

Effect of Jitmo spheric Air. — I now proceed to give you 
an account of the most conclusive experiments which I 
made whilst investigating the action of the insects, or their 
luminous segments only, on atmospheric air, and on oxy- 
gen. I placed in a small graduated bell-glass nine living 
glow-worms, and in another similar vessel, containing as 
much air, an equal number of detached segments. In 



LeCT. VIII. EFFECTS OF OXYGEN. 159 

twenty-four hours the insects no longer shone, though the 
detached segments were still feebly luminous. The air 
which remained under the glasses was analyzed thirty- 
six hours after ; and it was found that the oxygen had 
entirely disappeared, and was replaced by an equal volume 
of carbonic acid. In 11*8 cubic centim. of atmospheric 
air, wherein the entire insects had been put, we found 2-4 
cubic centim. of carbonic acid. In the glass which con- 
tained the luminous sections, all the oxygen had not been 
absorbed. 

Effect of Chlorine. — The entire insects remained lively 
and glowing in chlorine, quite as long as the separated 
segments; but when life and phosphorescence had disap- 
peared, they were neither restored by introducing air or 
oxygen, nor by applying heat. The insects, and their 
segments even, when crushed, no longer evinced phospho- 
rescence. 

Glow-worms which have been lel> for twenty-four hours 
in atmospheric air contained in a bell-glass, became slightly 
luminous for a few moments when they were warmed by a 
lamp. 

Effects of Oxygen. — I put some living and glowing worms 
into some bell-glasses filled with oxygen gas over mercury; 
they lived for about forty hours, and during the whole time 
continued to glow. 

I placed ten luminous segments, taken from ten living 
glow-worms, in pure oxygen. The segments continued to 
be phosphorescent for four whole days, and we saw them 
luminous, even during the day, when we looked at them in 
a dark place. The gas left in the glass was one-third car- 
bonic acid, and two-thirds oxygen. 

I put some other luminous segments into this oxygen, 
after having deprived it of the carbonic acid by means of 
potash, and again observed the same result. The seg^ 



160 PHOSPHORESCENCE. LeCT. VIII. 

ments which were there during four days, emitted, after 
that time, no more light, even when warmed. 

Here are the numbers deduced from some experi- 
ments: — 

Cubic Centim. Cubic Centim. 
Volume of oxygen gas, in which the entire 

glow-worms were placed . . . • • 6*8 

Volume of gas at the end of thirty hours . . . 6*.2 

Carbonic acid, absorbable by potash 4*2 
Oxygen gas, not absorbable by potash 2*0 

62 

Loss [ascribed to the absorption of carbonic 

acid by water on the bodies of the insects] . . 0*6 



The residual gas was oxygen, which disappeared by a 
small piece of phosphorus, leaving only a very small bub- 
ble of air. 

Other glow-worms were placed in 11*8 cubic centim. 
of atmospheric air. After thirty-six hours, the volume of 
air was unchanged, but it contained 2-4 cubic centim. of 
carbonic acid. 

The phosphorescent segments of some glow-worms were 
put into 6 cubic centim. of oxygen ; in twenty-four hours 
we analyzed the gas, whose volume was reduced to 5*8 
cubic centim., and we found that it contained 2 cubic 
centim. of carbonic aid, the remainder being oxygen. In 
all these experiments I invariably operated upon eight or 
ten segments taken from eight or ten different glow-worms. 

Effects of Oxy-hydrogen Gas. — I also observed that in a 
mixture of 9 parts of hydrogen, and 1 oxygen, these in- 
sects continued to live and shine, even after twelve hours 
experimenting. I found that about half of the oxygen was 
replaced by an equal volume of carbonic acid. 



LeCT. VIII. MUTILATED INSECTS. 161 

Effects of mixed Oxygen and Carbonic Acid. — In a mix- 
ture of 1 part oxygen, and 9 carbonic acid, I found that 
these insects did not continue glowing longer than two or 
three hours ; and in twelve hours died. I proved that, the 
glow-worm can neither shine nor live long in a mixture of 
2 parts carbonic acid, and 1 part oxygen ; and that in this, 
also, a portion of the oxygen disappeeired after the insects 
had been there for some time. 

Carbonic acid gas appears to act on. them deleteriously. 
Luminous segments, introduced into the preceding mixture, 
yielded the same results, in regard to the duration of light, 
as entire insects ; but with this exception, that the ox}'gen 
absorbed, and the carbonic acid emitted, were in much 
smaller quantities, and only about a fourth of what we ob- 
tain with entire animals. The volume of gas which dis- 
appeared during the experiment, is owing to the small 
quantity of water introduced on the body of the insect, and 
which dissolves the carbonic acid formed. 

Mutilated Insects. — The observation of this remarkable 
fact, that glow-worms continue to live for several hours 
after being deprived of their luminous segments, induced 
me to make a curious experiment, the result of which 
agrees with that already stated. 

I introduced twenty living and very brilUant glow-worms 
into a bell-glass, inverted over mercury, and containing 
Q'Q cubic centim. of pure oxygen gas. I carefully re- 
moved the luminous segments from twenty other living 
and very phosphorescent glow-worms, and put the insects 
thus mutilated into another bell-glass, also inverted over 
mercury, and containing 5*6 cubic centim. of pure oxygen 
gas. Lastly, the remaining twenty luminous segments of 
the last mentioned insects, were placed in a third graduated 
bell-glass, with 9 cubic centim. of ogygen, in the same 
manner as the preceding. In ten hours I examined the 
11 



162 PHOSPHORESCENCE. LecT. VIII. 

three glasses ; in all the volume of gas had diminished, and 
certainly on account of the formation of carbonic acid, 
which was afterwards absorbed either by the humidity of 
the insectSj or by the film of w^ater which covered the mer- 
cury. Thus, in the first, the gas was 6-2 cubic centim.; in 
the second, 5-4 cubic centim.; in the third, the volume had 
not sensibly lessened. The entire insects were yet alive, 
and glowing ; the segments were equally phosphorescent ; 
and the mutilated or halved insects moved. In the first 
glass, after the absorption effected by potash, there re- 
mained 3-8 cubic centim. of oxygen; in the second, 3*7 
cubic centim.; in the third, 8-2 cubic centim. The potash 
had consequently absorbed 2-8 cubic centim. of the carbonic 
acid produced by the entire insect ; 1*9 cubic centim. of the^ 
carbonic acid proceeding from the insects deprived of the 
segments; and 0*8 cubic centim. of the acid yielded by 
the phosphorescent substance alone. In examining these 
numbers, it is curious to find that the two parts, into which 
the animal had been divided, should act separately with 
the same degree of intensity, as in the entire insect, as if 
they possessed a life in common.* 

I have repeated the experiment several times, and have 
always found, that the absorption effected by the entire in- 
sect surpassed, by a much larger quantity than the numbers 
cited, the amount of absorption of the demi-glow-worms and 
their luminous segments. I will relate another experiment, 
which led to the same results as the preceding. I intro- 
duced several glow-w^orms into a bell-glass, filled with 

* The reader will perceive that, while twenty entire glow-worms pro- 
duced 2'8 cubic centimetres of carbonic acid, the separated parts of twenty 
other animals produced only 2-7 cubic centimetres (1-9 + 0-8) of this gas. 
The difference, therefore, is 0*1 of a cubic centimetre, and is probably 
referable to the absorption of a portion of the gas by moisture on the por- 
tions of the mutilated animals. — J. P. 



LeCT. VIII. MUTILATED INSECTS. 163 

livater, and inverted over the hjdro-pneumatic trough. In 
twenty minutes, the insects ceased to glow ; but immedi- 
ately after the introduction of some bubbles of air, they re- 
turned to life, and again became luminous. I repeated this 
several times, with the same insects. I repeated the expe- 
riment with water, which I had previously boiled for tw^o 
hours. In this liquid, the insects evolved light during ten 
or twelve minutes only. It is remarkable, that with other 
liquids than those which act chemically upon the substance 
of the insect, the duration of the phosphorescence should be 
different. In alcohol and ether, the phosphorescence lasts 
a little longer than in water ; in oil, on the contrary, its 
duration is less. It is necessary to proceed in the way I 
have here indicated, and not to confine oneself to placing 
the insects in the liquid contained in a capsule. In each 
of these last experiments, I believe that the duration of the 
phosphoresence ought to be, in part, attributed to the air, 
which always remains adherent to the insect. 

I tried another experiment, which, I think, I ought to 
describe to you, before deducing from the preceding, their 
necessary consequences. I separated the segments of se- 
veral very lively glow-worms, and then crushed and rubbed 
them in a small agate mortar. By treating them thus, the 
matter of the segments at first appeared very luminous ; but 
after a few seconds, the phosphorescence diminished, and 
then entirely ceased. This result was accelerated, when 
the mortar was moderately warmed. I placed at the bot- 
tom of a bell-glass, one portion of the triturated substance 
of the segments, and at the moment when it ceased to shine, 
I filled the glass with mercury, inverted it over the trough, 
and introduced oxygen. On contact with this gas, I saw 
once, and only once, amidst numerous experiments which 
I made, a very faint light, but which ceased in an instant. 
In another experiment, in which the triturated matter also 



164 PHOSPHORESCENCE. LeCT. VIII. 

shone feebly, when the gas was introduced, the light con- 
tinued for some time. In both of these cases, I analyzed 
the gas forty-eight hours afterwards. Its volume had not 
varied, and the absorption by potash did not exceed 0*2 
cubic centim. in 8 cubic centimetres of oxygen gas, in the 
experiment where the light had continued; and in the other 
there was no absorption ; the oxygen remained apparently 
pure. 

In another experiment, I heated twenty luminous seg- 
ments to + 40° Reaumur [=122° Fahr.], by putting the 
tube, in which they were contained, into water of this tem- 
perature. The segments became red, and ceased to glow. 
I then filled the tube with mercury, and, inverting it over 
the trough, introduced oxygen. I perceived no light ; and 
after four days the potash absorbed nothing. These seg- 
ments had not evolved light; oxygen had not been absorbed ; 
and consequently carbonic acid had not been produced. 

Effects of Sulphuretted Hydrogen. — Some glow-worms, 
put into sulphuretted hydrogen, quickly ceased to glow and 
to live ; and they did not afterwards become phosphores- 
cent, by placing them in contact with oxygen, or by warm- 
ing them. Some of the luminous, segments evolved a very 
feeble light when they w^ere crushed. 

Effects of Rarifed Air. — I will describe, lastly, the 
experiment of putting these insects in highly rarefied air. 
I placed, in the closed extremity of a long glass tube, some 
entire glow-worms, and the luminous segments of others. 
I filled the tube with mercury, and inverted it over a trough, 
filled with the same liquid as in the construction of a baro- 
meter. The glow worms and their segments were thus 
contained in a space where the air was very rarefied. The 
light ceased in the insects and in the segments almost at 
the same time; that is to say, the phosphorescence was ex- 
tinguished in hath iu the course of two or three minutes, 



LeCT. VIII. CONCLUSIONS. 165 

and, as usual, the intermittence first ceased. When I in- 
troduced air, immediately on the disappearance of the 
phosphorescence, this phenomena recommenced. In this 
case, I very distinctly saw all the glow-worms recover the 
faculty of motion which they had lost ; so that though they 
had ceased to shine in rarefied air, they were not dead. 
The same thing occurred on cooling them. 

Conclusions. — These facts necessarily lead to the follow- 
ing conclusions, — conclusions which are either entirely new, 
or more rigorously deduced from experiment, than any that 
have hitherto been published : — 

1st. The phosphorescence of the glow-worm may cease, 
without the insect being dead. 

2dly. There exists in this insect a matter which evolves 
light, without any appreciable heat ; and the animal, to 
manifest this property, does not necessarily require either 
to be entire, or to possess life. 

3dly. Carbonic acid and hydrogen form a medium in 
which the phosphorescent matter of the glow-worm ceases 
to shine after an interval of time, not exceeding thirty or 
forty minutes, provided that the gases are pure. 

4thly. In oxygen gas, the brilliancy of the phosphores- 
cent matter is considerably greater than in atmospheric air, 
and the duration of the phosphorescence is nearly three 
times as long. This holds good with regard to the luminous 
segments only, as well as with the entire animal. 

5thly. This phosphorescent matter, placed under condi- 
tions suitable for the emission of light, absorbs a portion of 
oxygen, which is replaced by an equal volume of carbonic 
acid. 

6thly. This same substance, when deprived of its faculty 
of glowing, and then placed in contact with oxygen gas, no 
longer absorbs oxygen, or produces carbonic acid. 

Tthly. Oxygen mixed with either hydrogen or carbonic 



166 PHOSPHORESCENCE. LeCT. VIIL 

acid, in the proportion of 1 to 9, forms a medium in which 
the phosphorescence continues for several hours. We may, 
therefore, conclude, that it is in consequence of some altera- 
tion in the phosphorescent matter, that this ceases to glow 
after it has been for some days in pure oxygen, one portion 
only of which has been replaced by carbonic acid. 

I examined the hydrogen in which I had kept several 
glow-worms for the space of twenty-four hours, and in 
which they had glowed for a few minutes only. The follow- 
ing is the result obtained when the gas was pure, and the 
experiment w^as conducted over mercury; the bell-glass 
being carefully filled by inverting it two or three times, in 
order to get rid of all the air adhering to the glow-worms ; 
the volume of the gas was slightly augmented : with 8 cubic 
centimetres of hydrogen, I obtained an excess of 0*2 cubic 
centim. which w^as absorbed by potash. Thus, then, the 
insects produce carbonic acid, which must either be formed 
by the union of carbon with the oxygen remaining in the 
trachese, or exist ready formed in the animals. When the 
luminous segments alone are placed in hydrogen, with due 
precaution, they glov;^ for a few seconds only and the gas 
is not altered. 

8thly. Heat, within certain limits, augments the light of 
the phosphorescent matter ; cold has a reverse effect. 

9thly. When the heat is too strong, the phosphorescent 
matter becomes altered, as it also does when placed in the 
air or in any gas w^hatever for a certain length of time. This 
undoubtedly is the reason w^hy these insects cannot live in 
all climates, and why they shine only during certain months 
of the year. 

lOthly. The phosphorescent matter, when thus altered, 
is no longer capable of emitting light or of becoming lumi- 
nous. / 

These conclusions evidently prove the nature of the 



LeCT. VIII CAUSE OF THE PHOSPHORESCENCE. 167 

phenomenon ; the production of light, by this insect, is 
essentially connected with the combination of oxygen with 
carbon, which is one of the elements of the phosphorescent 
matter. 

Cause of the P ho sp florescence. We must now inquire 
how the phosphorescence is produced in the living animal: 
under what circumstances it varies: and what is the struc- 
ture of the luminous substance and of the parts which sur- 
round it. 

JSTot due to Insolation. — I placed some very lively and 
shining glow-worms in a tin-box which closed accurately. 
I opened it twenty-four hours afterwards, it being then two 
hours after sunset. The insects appeared dead, but they 
still emitted a feeble light. By warming them in my hand, 
they began to move, and the light became more vivid. 

After thirty hours more, passed in this box, some of the 
insects were dead, and no longer glowed ; in others, slight 
phosphorescence was observed. This experiment supports 
the opinions of Beccaria, Mayer, and other philosophers, 
who regarded the phosphorescence of these insects as due 
to insolation. 

But here is another experiment, the result of which is 
clear and satisfactory. In the same box, which was pro- 
vided with a double bottom, I put, in one compartment, a 
great number of glow-worms, and in the other, a like quan- 
tity, intermixed with some fresh cut grass, gathered in the 
places where the insects had been found. At the expiration 
of twenty-four hours I examined them ; what I have before 
related had happened to the first, but the others were still 
lively and glowing. When we opened the box during the 
day, in a dark place, we perceived their phosphorescence. 
To avoid prolixity I shall content myself with saying, that 
for nine days I preserved the glow-worms, with which the 
grass had been intermixed ; and during this period they 



i68 PHOSPHORESCENCE. LeCT. VIII. 

continued alive and emitted much light. Thus, then, when 
the insect is placed in its natural conditions with regard to 
temperature, humidity, &c., and continues to be nourished, 
the phosphorescent matter is preserved independent of solar 
action. 

We conclude, therefore, from the preceding experiments, 
that the phosphorescent matter prepared by the animal, is 
preserved for some time luminous, although the animal be 
deprived of life; proving that life is not an indispensable 
condition of phosphorescence. By life, this substance is 
continually preserved with its properties entire, by the same 
process of nutrition which operates equally upon all parts of 
the animal. 

Agency of the JYervous System.' — I have not omitted to 
examine, what part the nervous system takes in the produc- 
tion of the phenomenon ; and I shall describe the experi- 
ments, made for this purpose, with all the necessary 
details. 

If, immediately after a glow-worm is caught, we place it 
on its back, and examine it, w^e perceive that the posterior 
abdominal segments are reddish green. During the day 
this colour is not so distinct, and is yellowish ; and the same 
thing occurs with glow-worms which have been dead a 
short time. During the life of the insect, the segments be- 
come, from time to time, luminous, and more or less fre- 
quently. By attentive observation made on many insects, 
it has been discovered that sometimes the hght does not 
appear at every part of the segments at the same time. If 
we slightly irritate any part of the insect, the hght becomes 
for an instant visible. By touching one of the points of the 
segments, the light continues longer. If, at this moment, 
we cut off the head of the animal, the light soon diminishes, 
afterwards entirely ceases, and then the red colour of the 
membrane of the luminous segments is very perceptible. 



LeCT. VIII. INFLUENCE OF POISONS. 169 

In this condition, we may strongly irritate the thorax of the 
insect without succeeding in producing phosphorescence. 
In order that this effect should take place, it is necessary 
to touch the luminous segments themselves; the irritated 
points then glow, and the light thus produced, goes on ex- 
tending itself over the untouched portion of the segments. 
If we perform this experiment by putting the insect upon 
the stage of the microscope, we can judge still better of the 
production and diffusion of the light. In order to succeed 
in this experiment, it should be made in the dark, and no 
light should be allowed to fall on the object. We perceive 
an extremely rapid oscillatory movement in the parts of the 
phosphorescent matter, and at the same time they become 
luminous. 

Influence of Poisons. — I have frequently tried the effect 
of nux vomica and opium, on the phosphorescence of these 
insects. For example, I dissolved 0-265 gramme of the 
extract of opium, or of the alcoholic extract of nux vomica, 
in 61 grammes of water, and placed the glow-worms in 
bell-glasses, filled with solutions thus prepared, and inverted 
over similar liquids. By proceeding thus, there was no 
contact with air. The results of a great number of ex- 
periments induce me to conclude, that the insects die, in 
the solution of nux vomica, eight or ten minutes sooner 
than they would in water. On the contrary, in the solution 
of opium, the phosphorescence continues eight or ten 
minutes longer than in water. I hope to be able to return 
to this object of our study, which I have now only glanced 
at, and which requires a greater number of experiments. 

I will add, that those glow-worms w^hich had ceased to 
shine in water, shone anew on contact with the air; whilst 
those which had been submitted to the action of nux vomica, 
or of opium, shone no more and died. Hence, the action 



170 PHOSPHORESCENCE. LeCT. VIII. 

of certain substances on phosphorescence is proved, though 
it is probable that they do not act by altering the phospho- 
rescent matter. 

I tried the effect of varnishing the abdomen only, of a 
great number of glow-worms with turpentine. I found 
that the light became weaker, and the scintillations fewer, 
but they did not entirely disappear. 

Microscopic Structure of the Luminous Organ. — I ex- 
amined the structure of the luminous organ by means of the 
microscope. On the removal of the luminous segments of 
the dorsal and abdominal membranes, there was perceived 
a yellowish, granular, globuliform matter, in which appeared 
groups of red globules, a great number of ramifications, and, 
moreover, a species of tubes which had the appearance of 
muscular fibre, but which, when closely examined, appeared 
hollow. 

By looking at them at night, the light was seen to be 
emitted by the granular yellow matter ; and when we com- 
pressed this between two glasses, the light w^as always 
observed on the edges of the examined portion. The ab- 
dominal membrane examined alone, after it has been 
washed several times in water in order to remove from it 
all the phosphorescent matter, is transparent, and furnished 
wdth a great number of hairs. The dorsal membrane, less 
transparent than the former, is likewise hairy, but it is also 
supplied, on its internal surface, with many tubes or trachese, 
which penetrate the phosphorescent matter. I must further 
add, that I never separated the abdomen of a glow-worm 
without finding under the last luminous ring but one, a 
bright red vesicle, which, viewed by the microscope, is 
found to be made up of a group of red globules. I have 
never met with this vesicle in other insects of the same 
genus, and no work on comparative anatomy mentions it. 



Lect. VIII. 



PHOSPHORESCENT MATTER. 



171 



In ray ignorance of this science I content myself with an- 
nouncing to zoologists the presence of this body.* 

Chemical JYature of the Phosphorescent Matter,' — I will 
not now detain you longer than is absolutely necessary, in 
our examination of the chemical nature of the phosphores- 
cent matter. This substance, taken from the living animal, 
has a remarkable odour, resembling that of the sweat of the 
feet. It is neither acid nor alkaline ; it dries readily in the 
air, appears to coagulate on contact with acids diluted with 
water ; does not perceptibly dissolve either in alcohol, or 
ether, or in weak alkaline solutions. It dissolves and be- 
comes changed, in hot concentrated hydrochloric and sul- 
phuric acids. By the employment of the last-mentioned 
acid, the solution does not become blue, which fact ex- 
cludes the idea of the presence of albumen. Heated 



* I subjoin figures of the luminous organs in two species of Lampyris, 
viz. L. lucida and L. noctiluca : the latter is the common glow worm of 
England. 

Fig. 9. 






Phosphorescent Organs of Glow-ioorms. 



No. 1. is an enlarged view of the in- 
ferior surface of the abdomen of the 
Lampyris noctiluca after the integument 
had been removed. 

a a a. Represent the three masses of 
luminous substances which are applied 
to the three last rings of the abdomen. 

bbb. The arrangement of cellular or 
intestinal substance on the other abdo- 
minal rings, which gives the pale colour 
to the body of this insect. 



Nos. 2. and 3. are tlie sacs of the 
common glow-worm, prodigiously mag- 
nified to show their structure. Fig. 3. 
is cut open to expose the luminous mat- 
ter it contains. The coat of the sac is 
still seen to preserve its figure. The sacs 
are formed of two layers or membranes, 
each composed of a transparent silvery 
fibre. The sacs are more minute than 
the head of the smallest pin, and are 
placed on the last abdominal ring.— J. P. 



172 PHOSPHORESCENCE. LeCT. VIII. 

in a tube, it gives out the usual ammoniacal products. It 
does not present any obvious trace of phosphorus ; of this 
fact I have assured myself, by calcining this matter several 
times with nitre in a platinum crucible, and by treating the 
dissolved residue with the tests which indicate the presence 
of the phosphates. From all that we have now stated, we 
can no longer regard the presence of phosphorus as the 
cause of the light in these insects. Perhaps by operating 
on a large number, we might succeed in discovering a slight 
trace of phosphorus, which is usually found in all organized 
substances. 

From all these experiments, I conclude that carbonic 
acid is produced by the contact with oxygen of the phos- 
phorescent matter alone, separated from the rest of the 
animal ; that the light ceases to be produced when this gas 
is not present, and that by the contact of the latter, light 
and a volume of carbonic acid, equal to that of the oxygen 
consumed, are produced ; and that the phosphorescent sub- 
stance of this insect, when not luminous, does not act on 
oxygen. 

It is, therefore, natural to suppose, that in the luminous 
segments of these animals, enveloped by transparent mem- 
branes, and by means of the numerous tracheae discovered 
here and there in these animals, atmospheric oxygen is 
brought in contact with a substance, sui generis, principally 
composed of carbon, hydrogen, oxygen, and azote. The 
presence of a great number of dispersed blood-globules 
intermixed with the granular luminous matter, proves that 
these segments are the centre of a peculiar organ of secre- 
tion ; and I believe that this red vesicle, which I have de- 
scribed as existing above the luminous segments, merits the 
attention of naturaUsts. Excitation and heat affect the 
phosphorescence, as they do all other phenomena of the 
animal economy, by directly favouring combustion ; and in 



LeCT. VIII. PHOSPHORESCENT ANIMALCULES. 173 

this way we account for the effects produced by some agents 
on the phosphorescent substance alone, when separated from 
the animal. The example of an organic substance which 
burns in the air by absorbing oxygen and emitting carbonic 
acid, is not new ; this is the case with decaying wood, vj'ith 
oiled cotton, with very finely divided charcoal, and many 
other substances liable to spontaneous combustion. If, in 
the case which now engrosses our attention, the heat which 
ought to accompany the chemical combination be wanting, 
it may be easily explained. The quantity of carbonic acid 
disengaged from the luminous segments of each of these 
insects in a given time, is so small that the heat developed 
cannot accumulate there. The phosphorescence of wood, 
to which I alluded just now, as well as many other cases 
in which an emission of light accompanies chemical com- 
binations, but which I need not farther notice, clearly prove 
that a disengagement of light may take place without any 
perceptible augmentation of temperature. Heat requires to 
be accumulated in order that its presence may be discovered 
by our instruments; and it is. in this way we explain our 
inability to detect heat in the animals termed cold- 
blooded. 

I have thought it my duty to enter thus fully into the 
peculiarities relative to the phosphorescence of the glow- 
worm, because I intend only slightly to allude to other 
cases of animal phosphorescence. 

Phosphorescent Animalcules. — Every one know^s, that 
during the night there is observed in the sea vast luminous 
tracts, which were formerly vaguely ascribed to the clash- 
ing of waves, to electricity, or to phosphu retted gases 
formed by the putrefaction of the mollusca. We now 
believe them to be owing to an immense number of phos- 
phorescent microscopic animalcules.. But no one knows 



174 PHOSPHORESCENCE LeCT. VIII. 

what are the physico-chemical conditions under the in- 
fluence of which these infusoria become phosphorescent. 

Phosphorescence of Putrescent Fish. — There can be no 
doubt that fish, by putrefaction, become luminous ; and 
from this circumstance may perhaps, in some cases, be pro- 
duced the phosphorescence of the sea. The few experi- 
ments which I have made, prove that in a vacuum, or in 
carbonic acid, this phosphorescence ceases, but recom- 
mences in the air. 

Phosphorescence of the Human Body. — In the annals of 
medicine, there exist well established facts of the appear- 
ance of flames upon the bodies of persons affected with 
certain diseases. 

Phosphorescent Perspiration. — A phosphorescent perspi- 
ration of the feet has been spoken of, and it is curious to 
observe the analogy which exists between the odour of the 
phosphorescent substance of the glow-worm and the sweat 
of the feet. All these cases of phosphorescence remain 
unexplained. 

Phosphorescence ofAnnelides and Ophiurce. — I cannot con- 
clude this lecture without mentioning to you the important 
observations recently made by Quatrefage, upon the phos- 
phorescence of the Annelides and the Ophiurce. This dis- 
tinguished naturalist has observed with the microscope, that 
the phosphorescence of these animals belongs to the mus- 
cular fibre, is intermittent, and becomes more vivid when 
the fibre is irritated ; and after repeated contractions, ceases 
for a certain time, being reproduced if the animal be left to 
repose. 

Here is a point of analogy that you ought not to lose sight 
of. The life and the functions of muscles are accompanied 
by the disengagement of heat and of light, and these func- 
tions are immediately dependent on the nervous agent. It 



Lect. VIII. of plants. 175 

is very desirable that the observations of Quatrefage should 
be confirmed and varied. 

Phosphorescence of Plants. — Botanists assert, that in many 
plants inflorescence is accompanied by phosphorescence. 
But this phenomenon is, also, too rare to be capable of be- 
ing properly studied. During the period of inflorescence, 
oxygen is absorbed and carbonic acid disengaged ; in a 
word, there is combustion, and this is the reason why in 
certain cases of inflorescence considerable heat is developed. 
Perhaps, also, some volatile oil, separated from the flower 
at the ordinary temperature, may be the cause of this light. 



176 MUSCULAR CURRENT. LeCT. IX. 



LECTURE IX. 

ELECTRICAL CURRENT OF MUSCLES. 

Argument. — The chemical actions going on in living beings develop 

electricity as well as heat and light. 
The galvanoscopic frog. 
Demonstration of the existence of an electrical current in the muscles of 

recently killed, as well as of living frogs and other animals. 
The muscular pile ; its construction ; the direction of the current produced 

by it is from the internal to the external surface of the muscle ; the in- 

tensity of its current is proportionate to the extent of the series. 
The electric current of other tissues and organs. 
Agency of the nervous system in the production of the muscular current. 

Influence of the organic condiiions of the muscles; intensity of the cur- 

rent in starved, in well nourished, in inflamed, and in engorged muscles . 

influence of temperature on the current; modifications produced by 

poisons. 
Piles formed with muscles and their connected nerves. Origin of the 

muscular current; Liebig's hypothesis; objection to it. 

Heat and Light evolved in the Organism. — In the pre- 
ceding lectures, I have clearly proved that in animals there 
is a constant production of heat, and in some cases, of light 
also. Guided by experiments and evident analogies, we 
have been forced to attribute the disengagement of heat and 
of light, in the living organism, to chemical actions which 
take place there ; and the result of this investigation has 
been, the discovery of a fresh proof of the constancy of the 
general effects of the great forces of nature. The facts 



LeCT. IX. GALVANOSCOPIC FROG. 177 

which will form the subject of the present lecture, also lead 
us to the same conclusions. 

Electricity evolved also, — It would be absurd to suppose 
that the chemical actions of living beings, all of which de- 
velop heat, and often light, would not be accompanied by 
the production of electricity. This emission of electricity, 
which we have now to demonstrate by all the evidence 
proper to chemical truths, will form the subject on which I 
am about to address you. 

Here is a very simple and easily executed experiment, 
which proves the existence of an electrical current, which 
is produced when we connect, by means of a con- 
ducting body, two different parts of the same muscular 
mass, belonging either to a living animal or to one recently 
killed. 

Galvanoscopic Frog. — A frog is prepared according to 
the usual method of Galvani ; that is, we cut it through the 
middle of its pelvis, separate carefully all the muscles of the 
thigh, and divide one of the lumbar plexuses as it passes 
out of the vertebral column. We then have a leg of the 
frog united to its long nervous filament, composed of the 
lumbar plexus, and of its prolongation in the thigh, that is( 
to say, of the crural nerve. The frog, thus prepared, and 
w^hich I have called the galvanoscopic frog, is very useful 

Fig. 10. 



The Galvanoscopic Frog. 

in researches on the electric current. For this purpose we 

introduce the claw of a frog into a glass tube covered with 
12 



178 MUSCULAR CURRENT. LeCT. IX. 

an insulating varnish, take hold of the tube with the hand, 
and afterwards bring any two parts of the body, whose 
electric state we wish to examine, in contact with two dif- 
ferent and sufficiently distant points of the nervous filament 
of the galvanoscopic frog. 

If we take the precaution of not touching the body with 
any portion of the muscle of the leg, and if the limb be well 
insulated from the hand, w^e may be certain that the con- 
traction which the galvanoscopic frog suffers, is due to a 
current produced in the body touched, and that the nerve 
only conducts it, and renders it evident by the contraction 
of the muscle. 

Electric Current in Muscles. — Furnished wdth a frog, thus 
prepared, I take a living animal, a pigeon for example, 
slightly cut its pectoral muscle, after having carefully re- 
moved the integuments, and introduce into the wound the 
nerve of the galvanoscopic frog. 

You observe the contraction of the frog. If you reflect 
on the arrangement, you will be satisfied that it is absolutely 
necessary to touch two distinct parts of the pectoral muscle 
of the pigeon, with two different parts of the nervous fila- 
ment. If I apply the extremity of the nerve to the bottom 
of the wound, and another portion of the nerve to the lips 
of the wound, or, better still, to the external surface of the 
muscle, the frog continually contracts. This experiment 
clearly demonstrates the presence of an electrical current, 
w^hich circulates in the nerve, since it is necessary to form a 
circuit in which the nerve forms a part. If you have any 
doubt that the contractions of the frog are really excited by 
a current due to the different parts of the muscle of the ani- 
mal, you will soon be convinced, by finding that no con- 
tractions are produced when I touch two different parts of 
the nerve with one liquid, or with a perfectly homogeneous 
conducting body. 



LeCT. IX. CURRENT IN LIVING ANIMALS. 179 

Do not suppose that the blood is more apt than any other 
conducting liquid, to excite contractions in the muscle of 
the galvanoscopic frog. I let fall a drop of the blood of 
this same pigeon upon a glass plate, and place two distinct 
parts of this drop in communication with two points of the 
nerve of the frog, but it evinces no contraction. 

It is useless to show you, that if I moisten either the 
nerve of the frog, or the different portions of the muscle of 
the pigeon, with a saline or acid solution, or, still better) 
with an alkaline one, the contractions of the frog are more 
energetic than in the former experiment. These solutions 
act chemically on the substance of the nerve, or of the 
muscle. 

The phenomenon which you have witnessed in the pi- 
geon, takes place in every other animal, whether warm or 
cold blooded. 

I have recently proved, that the galvanoscopic frog gives 
the same signs when we operate upon a wound made in 
the muscle of a man. 

Contractions are also produced in the frog when we bring 
the nerve in contact with a muscle separated from an ani- 
mal. Here is a thigh of a frog, detached some time since 
from the body of the animal. I make an incision into the 
crural muscle, and connect the extremity of the nerve of the 
galvanoscopic frog with the bottom of the wound, and 
another point of this same nerve with the surface of the 
muscle. You immediately perceive that the frog suffers 
contractions ; you will observe that it will also do so if I 
repeat this experiment with the thigh of the pigeon or rab- 
bit, or with a piece of an eel. But if I continue the expe- 
riment by renewing from time to time the galvanoscopic 
frog, we perceive that the phenomenon soon ceases, if we 
employ the muscles of the pigeon or of the rabbit, whilst it 
continues longer with those of the frog and the eeh 



180 MUSCULAR CURRENT. LeCT. IX. 

The contractions which you have seen excited in the gal- 
vanoscopic frog, already give you an idea of an electric 
current, which I shall call muscular; which, derived from 
the muscle of a living or recently killed animal, in which it 
is produced, circulates in the nerve of the frog. 

But it is necessary to have recourse to the galvanometer 
to place beyond doubt the existence of this current, to dis- 
cover its direction, and to determine its intensity relatively 
both to the condition of life or death, and to the position of 
the animal in the scale of beings ; in a word, to study its 
laws. 

I expose the pectoral muscle of a living pigeon, I make 
a wound in it, and quickly convey the two platinum ex- 
tremities of a very dehcate galvanometer, the one to the 
external surface of the muscle, the other to the interior of 
the wound. You perceive that the needle instantly de- 
viates from 15°, to 20°, and even more ; thus demonstrating 
the existence of a current, whose direction is from the in- 
ternal part of the muscle to the surface of the same muscle. 
The needle soon comes back, and oftentimes returns to 0°. 
If I remove the extremities of the galvanometer from within 
the wound, and then a moment afterwards recommence 
the experiment, it sometimes, or rather, most frequently 
happens, that I obtain a new deviation in the direction of 
the first, but always more feeble. In some cases, however, 
the succeeding deviations are in the reverse direction of 
the first ones. By repeating the experiment on the muscles 
of other animals, the first indication furnished by the gal- 
vanometer is obtained, in most instances, like that which 
we have witnessed ; but it is right to say that afterwards, in 
the succeeding experiments, the currents are often inverse 
to the first. Such a fact, then, is not very clear: it does not 
rigorously prove the existence of the muscular current. If 
l had experimented ia like manner on a dead animal, you 



LeCT. IX. MUSCULAR PILE. 181 

would have seen, as usual, first, the signs of a current di- 
rected from the internal to the external part of the muscle, 
but less distinctly than in the living animal ; here, also, great 
uncertainty exists ; our experiments are not conclusive. 
There is, then, some defect in this mode of proceeding, and 
every philosopher accustomed to manipulations with the 
galvanometer will perceive this defect, and will recognise 
the causes of it. 

In one of my works, entitled, Traite surles Phenomenes 
Electro-physiologiques des Jlnimaux^ I have dwelt with some 
prolixity on the manner of applying the galvanometer to the 
study of the electric phenomena of animals, but it would 
occupy too much time to repeat here what I have there 
stated. 

I shall content myself with having shown you that I have 
succeeded in proving, by the aid of the galvanometer, the 
existence of the muscular current, and in discovering its 
fundamental laws. 

Muscular Pile.~^l take five or six frogs prepared after the 
manner (already mentioned) of Galvani; I cut them in halves, 
separate the thighs from the legs by disarticulation, and di- 
vide the thighs transversely into two parts. I thus obtain a 
certain number of the halves of thighs, from amongst which 

Fig. 11. 




The Muscular Pile. 

A. Positive end of the pile formed by the external surface of the muscle. 

B. Negative end of the pile formed by the internal surface of the muscle. 
The arrow indicates the direction of the current in the pile. 

I select those only which belong to the lower portion ; I 
arrange this series of demi-thighs upon a varnished tray, in 
"which are some cup-shaped depressions or cavities. The 
preceding figure will show the arrangement. 



182 MUSCULAR CURRENT. LeCT. IX. 

I first place one of these demi-thighs in such a manner 
that its external surface is contained in one of these cups. 
Next to this I place another, in such a position that its ex- 
ternal surface is in contact with the internal surface of the 
first; and in this way, one after the other, all the demi- 
thighs are arranged in a row, touching one another, and 
with the same surface always turned in the same direction. 
The last demi- thigh, like the first of the series, should be 
placed in one of the cups of the tray, but by its internal 
surface. 

Here, then, we have a pile of demi-thighs of frogs, of 
which one extremity is formed by the external surface of 
the muscle, the other by the internal surface. I fill the two 
cups with a weak saline solution, or even with distilled wa- 
ter; plunge into them the two extremities of the galvanome- 
ter, and immediately I observe a deviation of the needle, 
which before the immersion of these conductors was at 0°. 

Thus, then, the presence of an electric current produced 
by a pile formed of the muscles of the frog is demonstrated 
by the galvanometer. Vary the experiments as much as 
you like ; in lieu of the muscles of frogs, use the muscles 
of other animals, of fishes, birds, or mammals, and, pro- 
vided that you keep the relative position of the muscular 
elements, before pointed out, namely, the internal surface 
next to the external of the muscle, you will always obtain a 
deviation more or less great of the galvanometer needle : 
this deviation will indicate constantly^ by its direction, the 
presence of a current proceeding in the pile from the inter- 
nal to the external surface of the muscle. 

I must observe that the intensity of the current is in pro- 
portion to the number of demi-^thighs employed to form the 
pile. Here is a pile formed of ten demi-thighs ; the varia- 
tion of the needle is from 30° to 40° ; here is another with six 
elementSj and the needle marks from 10° to 20° ; in a 



LeCT. IX. AGENCY OF THE NERVES. 3b83 

third, composed of four elements, it deviates only from 6° 
to 8° at the utmost. The increase of the intensity of the 
muscular current, in proportion to the number of the mus- 
cular elements employed to form the pile, is constant, 
whatever may be the animal from which the muscles are 
taken. 

If, in place of arranging the elements in a straight line 
to form the pile, you dispose of them in such a way that 
they form a semicircle, and thus shorten the distance be- 
tween the poles, you may close the circuit with the single 
nerve of the galvanoscopic frog, and by its contractions in- 
fer the existence of the electric current. 

Currents in other Tissues. — I wished to ascertain whether 
the other tissues and organs of animals, the membranes, 
the nerves, the brain, the liver, and the lungs, denoted 
the presence of an electric current. I have invariably ob- 
tained very feeble signs of it. The heart alone gave indi- 
cations of a very strong current ; but, as you know, the 
heart is a muscle. 

It is unnecessary for me to tell you that I tried the 
analogous experiments on the membranes, liver, &c., by 
forming the pile with portions of these tissues or organs, 
as in the case of the muscles, and that I took the same 
precautions. 

Jigency of the JYerves, — Thus the current, of which we 
have hitherto spoken, is principally demonstrated in the 
muscles. This property does not depend on the nervous 
system. Many of the experiments which I made, and 
which are related in ray work, already alluded to, con- 
vinced me that if the nervous system which supplies the 
muscles be destroyed, the latter do not lose the property 
of manifesting the electrical current. I formed piles with 
muscles deprived of their nerves with every possible care ; 
with other muscles taken from frogs, a considerable part 



184 MUSCULAR CURRENT. LecT. IX. 

of whose spinal marrow I had destroyed some days be- 
fore with a red-hot iron, or which I had killed by opium ; 
but no perceptible difference was manifested between the 
intensity of the current produced by these piles and that of 
the current caused by the same number of muscular ele- 
ments taken from the entire frog. 

If you continue experimenting, by means of the gal- 
%'anometer, on a pile, which henceforth w^e shall call mus- 
cular, you will readily perceive that the deviations of the 
needle become more and more slight, and then cease en- 
tirely. And if you use piles formed of the muscles of ani- 
mals belonging to different classes, you will observe that 
the signs of the current diminish the more rapidly, and 
disappear the sooner, in proportion as the animal which 
you have been using occupied a more elevated position 
in the scale of beings. Thus it happens that piles formed 
by the muscles of fishes, frogs, and eels, give several hours 
after death, perceptible signs of the current; whilst those 
which are made with the muscles of birds and mammals, 
cease to do so at the end of a few moments. We have 
already noticed the uncertainty of the signs of the current, 
presented by the galvanometer, when the extremities of the 
wire of the instrument were put directly in contact with 
the muscles of the living animal. In this case, in order 
to be able to establish the facts in a more satisfactory 
manner, it becomes necessary to vary the mode of experi- 
menting. 

Here is an experiment which I have made, and which 
is free from all error; it is only the repetition, upon the 
living animal, of that w^hich I made upon the demi-thighs 
of the frogs. You can easily understand how we manage, 
with great care, to confine, on the tray before spoken of, 
a certain number of living frogs, by fixing there the four 
legs by means of four nails, and by placing them thus one 



LeCT. IX. ORGANIC CONDITIONS OF MUSCLES. 185 

after the other ; each one being deprived of the integuments 
of the thighs and the legs ; and moreover, an incision being 
made in the muscle of one of their thighs. 

The frogs being thus prepared, we easily succeed in put- 
ting the leg of one into contact with the interior of the 
muscles of the cut thigh of the next animal. In this way 
we form, with living frogs, the pile already described. 
The current which we then obtain is, as usual, directed 
from the interior to the external part of the muscle : its 
intensity is, with an equal number of elements, more con- 
siderable than with the muscles of dead frogs ; and it more 
slowly becomes w^eaker. 

When w^e connect the interior and the surface of the 
muscle, of a living or recently killed animal, by means of 
a conducting arc, the existence of an electric current is then 
rigorously demonstrated. This current is always directed 
from the interior to the exterior of the same muscle ; its 
duration after death varies, and is much longer in cold- 
blooded animals than in those of a higher order. It ex- 
ists without the direct influence of the nervous system, 
and it is not modified, even when we destroy the integrity 
of the latter. 

Influence of the organic Conditions of Muscle. — It remains 
for me to notice the investigations I have undertaken with 
the view of discovering the influence which the organic 
conditions of the living muscle have upon this current. 

When we examine the muscles of animals which have 
been kept without food, or in which the blood either circu- 
lates slowly, or is entirely interrupted, we see that the cur- 
rent has lost much of its intensity. The same effect is 
produced by employing frogs which have been left for some 
time in water, more or less deprived of air by ebullition. 

If, on the contrary, the muscles have been for some time 
the seat of inflammation, or have been gorged with blood, 



186 MUSCULAR CURRENT. LeCT. IX. 

or belong to animals that have been well fed, the muscular 
current shows more intensity, and continues for a longer 
period. 

I have especially experimented upon frogs, because these 
animals are more capable of resisting the suflerings to which 
they are subjected, in these researches, than other animals. 

If the muscles of which the pile is composed belong to 
frogs that have been submitted for a long time to a very loW 
temperature, namely, to 0° centig. [ = 32° Fahr.], or even 
above 0°, the current will be found to be very feeble. In 
warm-blooded animals, the difference occasioned by a re- 
duced temperature is less perceptible than in frogs. One 
result may perhaps at first surprise you. It is that the 
muscular current has the same intensity whether the pile be 
constructed of single demi-thighs of frogs, or of the same 
number of elements, each of which consists of two or more 
demi-thighs laid one on the other. In other words, the 
superficies of the elements has no influence on the intensity 
of the current. The same happens with piles formed of 
conductors of the second class, namely, with acid and alka- 
line solutions, which react on one another. 

Influence of Poisons^ <Src. — I wished to see whether the 
action of poisons had any effect on the intensity and dura- 
tion of the muscular current; and I found that the intensity 
of a current obtained from frogs poisoned by carbonic acid, 
hydrocyanic acid, and arseniuretted hydrogen, did not differ 
from that furnished by unpoisoned animals. 

The influence of sulphuretted hydrogen on the intensity 
of the current, is, on the contrary, very marked; a fact 
which I have verified several times, both upon frogs and 
pigeons asphyxied and killed in this gas. A dead animal, 
in an atmosphere of sulphuretted hydrogen, almost entirely 
loses the property of manifesting the existence of the mus- 
cular current. 



LeCT. IX. PILE OF LIVING PIGEONS. 187 

I have before told you, that in the muscles of frogs 
killed by narcotics, the current was as strong as in those 
which had not been destroyed in this manner. 

Piles of Muscles with JYerves attached. — A word also on 
the results obtained by investigating the muscular current 
in muscles whose nerves are left entire, and thus submitted 
to experiment. 

I formed some piles of the halves of frogs, in w^hich, 
however, the muscles did not directly touch each other ; 
the communications between them being established by 
the nervous filaments. I invariably found that the direc- 
tion of the current was not changed, its intensity alone be- 
ing diminished. In all, according as the contacts took 
place by the nervous filaments above the incision in the 
thigh, or by the filaments of the leg which was left con- 
nected with the thigh, the direction of the current being 
the same, the current was from the nerve towards the mus- 
cular element, sometimes in the contrary direction : in 
other words, the nerve having no influence upon the di- 
rection, always acted by representing the electric condition 
of the surface of the muscle, whether internal or external, 
with which it was in contact. 

In these cases the current was weakened by the imper- 
fect conducting power of the nerve, and if in place of the 
latter, we employ a cotton thread soaked in distilled water, 
the results are identical w4th those obtained by using the 
muscles with the nerve. 

Pile of living Pigeons, — I may add that I have recently 
succeeded in forming a muscular pile with living pigeons, 
similar to that made of living frogs. In comparing these 
piles with one another, I found that the first signs of the 
muscular current were stronger in the pile of pigeons than 
in the frog pile. The difference is, in fact, greater when 
we consider that in the pigeons the resistance of the cir- 



188 MUSCULAR CURRENT. LeCT. IX. 

cuit is much more considerable than in that of frogs. I 
have proved that the muscular current always becomes 
mbre rapidly weak, and ceases sooner, with pigeons than 
with frogs. 

Muscular Piles in Gases. — Lastly, I have to state that the 
current produced by a certain number of muscular elements 
had the same intensi-ty, and was of the same duration, when 
the elements were placed in hydrogen, oxygen, carbonic 
acid, and air more or less rarefied. 

Sources of the muscular Current. — From all that we have 
stated in this lecture, it follows that* the existence of an 
electric current in the muscles has been well demonstrated, 
and that its principal laws are established. The origin of 
this current resides in the electric conditions w^hich are 
produced by the chemical actions of the nutrition of the 
muscle. The blood charged with oxygen, and the muscu- 
lar fibre, which becomes transformed on contact with this 
liquid, compose the elements of a pile : they are the liquid 
acid and zinc. In the normal condition of the muscle, 
there can only be molecular currents produced by the for- 
mation and destruction of opposite electrical conditions in 
the same points ; but if a great number of points of the 
muscular fibre be put, by means of a good conductor, in 
communicatioti with others of a diflferent nature, which do 
not suffer the same chemical action on the part of the 
blood, the electric current should then circulate. It is 
this fact, furnished to us by experiment, which proves at 
the same time the development of electricity in the living 
muscle, and the impossibility for the electric current to 
circulate in the masses of this muscle in the natural con- 
dition. 

Liebig^s Hypothesis untenable. — Liebig, finding a free 
acid in the substance of the muscle, and knowing that the 
blood and lymph are alkaHne, fancied that he could ex- 



Lect. IX. liebig's hypothesis untenable. 189 

plain the muscular current by saying that it is due to the 
combination of the acid with the alkali of the blood. But 
it is obvious that, on this hypothesis, the laws of the mus- 
cular current which we have given, cannot be understood. 
Weak acid and alkaline solutions are found in the tissues 
of animals where there is no electrical current. [The 
muscular current, whose direction from the interior to the 
surface of the muscle is constant, whose intensity and du- 
ration varies in a constant manner in mammals, birds, rep- 
tiles, &c., and which is destroyed by sulphuretted hydro- 
gen, and by want of respiration, does not admit of so vague 
an explanation, and one so little founded in fact.*] 

* The passage within brackets is a translation from a notice by Mat- 
teucci in the Comptes Rendus, March 15, 1847.— J. P. 



190 ELECTRIC FISHES. LeCT. X. 



LECTURE X. 

electric fishes. — proper current of the frog. 

Argument. — Electrical plienomena peculiar to certain animals. 

Electric Fishes. Number of them known. The torpedo has been most 
frequently studied. 

Torpedo ; the shock produced by it ; electrical phenomena of the discharge . 
Electric organs ; direction of the current; physiological function of the 
discharge ; influence of electricity, mechanical injury, heat, and chemi- 
cal agents on the electric organ. Nervous system of the torpedo ; the 
electric lobe of the brain. Analogies between muscular contractions 
and the discharge of the torpedo. 

Gymnotus ; Humboldt's description of the mode of catching electric eels ; 
Faraday's experiments on the gymnotus; direction of the current. 

General structure and composition of the electric organs of fishes; hypo- 
thesis of their action and of the influence of the nerves on them. 

Silurus ; position of its poles. 

Proper current of the frog ; discovered by Galvani; is a phenomenon be«- 
longing to all animals; its direction; has a common origin with the 
muscular current. 

In the preceding lecture I have shown yon that elec- 
tricity is developed in the living muscular fibre, by the 
chemical actions going on there ; and that by properly con* 
ducted experiments it may be rendered manifest. The 
muscular current is a general property of the living or- 
ganism. To-day I proceed to bring under your consi- 
deration the development of electricity peculiar to certain 
animals. 

Electric Fishes. — We are acquainted with five different 
fishes which are endowed with this property: the Raia 



LeCT. X. PHENOMENA OF THE TORPEDO. 191 

Torpedo* the Gymnotus eledricus^ the Silurus eledricus, 
the Tetrodon eledricus, and the Trichiurus eledricus. Two 
only of these, the torpedo and the gymnotus, have been 
carefully examined ; and the first, in particular, having been 
the object of numerous researches, will be the special sub- 
ject of our lecture. 

Eledric Phenomena of the Torpedo. — If we grasp a living 
torpedo with the hands, a strong shock is felt in the wrists 
and arms, like that produced by a voltaic pile of from a 
hundred to a hundred and fifty elements, charged with salt 
and water. If we continue to hold the animal between the 
hands, the shocks succeed each other, sometimes with so 
much rapidity that it soon becomes impossible to sustain 
them ; but after the lapse of a certain time the animal loses 
its vivacity, and the shocks become less energetic, even 
when we may have taken the precaution to hold the animal 
in a vessel filled with salt water. Direct contact with the 
animal is not requisite, as the shock is sufficiently strong to 
be felt without it. The [Neapolitan] fishermen are well 
acquainted with this fact, and learn the presence of the 
torpedo amongst the shoal in their nets by the shocks which 
they experience, especially in the arms, when they wash 
the captured fishes by dashing bucketfuls of water over 
them. In the water containing the torpedo the shock is 
felt at considerable distances. The animal appears to be 
endowed with this faculty to enable it to kill the fishes on 
which it feeds. 

Identity of the Power of the Torpedo and that of Elec- 

* Under the Linnean name of Raia Torpedo have been confounded 
several distinct species row referred to the genus Torpedo. Three species 
of torpedo are found in tlie Italian t-eas ; viz. T. Galvani, T. Narce, and 
T. Nohiliana. The first two were included under the Linnean name of 
Raia Torpedo. The torpedo whose electrical organs were described by 
Hunter was the T. Guloani. — J. P. 



192 ELECTRIC FISHES. LeCT. X. 

tricity. — The earliest observers soon perceived the identity 
of the phenomenon presented by the torpedo with the elec- 
trical discharge : they found that when the animal was in- 
sulated, no shock was felt by touching it with sticks of 
sealing-wax, glass rods, &c.: but it was immediately felt 
when they employed, instead of resin or glass, water, wet 
cloths, or better still, metallic bodies. Walsh went still 
farther : he demonstrated by experiments, the accuracy of 
which are generally admitted at the present day, that the 
two opposite surfaces of the body of the torpedo are the 
poles, at which the opposite electricities are found at the 
moment of the discharge. It follows, therefore, that the 
greatest possible shock is obtained by connecting the belly 
and the back of the fish, by means of a conductor, which 
may be the body of the observer. At one time it was 
thought that, in order to obtain this shock, it was sufficient 
to touch, with a conductor, any part whatever of the back 
or the belly of the animal; and, consequently, that it was 
unnecessary to make the connexion, which we have spoken 
of, between the two opposite surfaces of the fish. But it is 
now clearly proved that this condition is indispensable, and 
that if we succeed in getting a shock by touching the 
animal, at a single point, with a metallic conductor held in 
the hands, it must be in consequence of the torpedo not 
being insulated, whereby the circuit is completed through 
the ground and the body of the observer. If, however, the 
torpedo be insulated by placing it, with one of its surfaces, 
on a resinous plate, a slight shock is obtained when we 
touch the other surface with the finger. This phenomenon 
will be fully understood when we shall have explained to 
you the laws of the distribution of electricity, on the body 
of the animal, at the moment of its discharge. 

Phenomena of the Shock. — The shock of the torpedo is 
accompanied by all the phenomena proper to the electric 



LeCT. X. PHENOMENA OF THE SHOCK. 193 

discharge or current. Frogs, prepared after Galvani's 
method, and arranged upon the body of the torpedo, suffer 
contractions at each shock which this animal gives, on being 
excited. The same effect takes place even when the frogs 
are put at some metres [yards] distant from the torpedo, 
provided that they, as well as the torpedo, are placed on a 
wet cloth. If the frog, prepared in the way stated, be held 
in the hand, and brought, by means of the extremity of its 
nerves, in contact with a point of the body of the torpedo, 
it suffers contractions at each shock from the fish; but they 
cease when the torpedo is insulated, or when the frog is 
suspended by means of an insulating thread. Notwith- 
standing this precaution, contractions take place when a 
long portion of its nervous filament is spread over the body 
of the torpedo. This fact is analogous to that of receiving 
the shock in the fingers when the torpedo is insulated. 

When we distribute several frogs over many points of 
the surface of the torpedo, at first all of them contract at 
each discharge of the fish ; but, in proportion as its vigour 
lessens, we perceive that those frogs which suffer contrac- 
tions for the longest time are those placed upon the sides of 
the animal near the head: in other words, the points which 
preserved the faculty of making the frogs contract for the 
longest period, are those which correspond to two peculiar 
organs, situated laterally and symmetrically towards the 
cephalic extremity of the fish. When the two extremities 
of the platinum wires of a moderately sensible galvanometer 
are placed in contact with the back and belly of the torpedo, 
and the animal is irritated in order to obtain the discharge 
we observe, that at the moment when the frogs contract, the 
needle of the galvanometer deviates suddenly, then im- 
mediately returns back, oscillates, and stands at 0°, even 
though we continue to keep the circuit closed. When 
a fresh discharge from the fish occurs, the same phenome- 
13 



194 



ELECTRIC FISHES. 



Lect. X. 



non is repeated. By the aid of this instrument we are 
enabled to prove that, in the discharge of the torpedo, the 
current is directed in the galvanometer from the back to the 
belly of the fish, so that the back represents the positive 
pole, and the belly the negative pole of the pile. If, by 
means of the extremity of the wires of the galvanometer, 
we examine different parts of the body of the torpedo at 
the moment when the discharge takes place, we perceive, 
in a manner still more evident than when frogs are used, 
that, at the commencement of the experiment, the signs of 
the current are obtained, by establishing the circuit between 
any part of the back and of the belly; but when the animal 
has become weakened, it is necessary for those parts of the 
body which correspond to the points called the electric 
organs, to be touched, in order that the existence of the 
current may be made manifest.^ 



Fig. 12. 




Torpedo with one of its Electric Organs exposed. 

It is curious to observe that, by simultaneously touching 
two points of eithLer the abdominal or diorsal surface of one 



LeCT. X. PHENOMENA OF THE SHOCK. 195 

of these organs, that the signs of the current are percepti- 
ble, but less evidently so than when the circuit has been 
established between the two opposite surfaces. In order to 
produce the deviation of the needle, by touching with the 
galvanometer wires two points belonging to the same sur- 
face of the fish, it is indispensable that one of the wires 
should be in contact with a part near the periphery of the 
electric organ, and that the other should occupy a point 
almost diametrically opposite to that of the first. We then 
have signs of the current which always passes in the gal- 
vanometer, from the wire nearest to the median line of the 
animal to that which is the most distant from it: we also 
obtain them with the galvanometer, by keeping one of the 
wires in contact with the abdominal or dorsal surface of one 
of these organs, and by introducing the other into the inte- 
rior of the organ itself. The current is invariably directed 
from the wire which touches the dorsal surface, or that 
which is nearest to it, to the other wire. These facts ex- 
plain the feeble shock experienced by touching with the 
finger the insulated torpedo. 

If, instead of the conductor of the galvanometer, we use 
a metallic wire, one portion of which is bent into a spiral, 
with an [unmagnetised] steel needle introduced within it, 
and then touch the two surfaces of the torpedo with the ex- 
tremities of the wire, the discharge magnetises the needle. 
The direction of the magnetism produced by the discharge 
of the fish is constant; that is to say, it is the same as that 
indicated by the galvanometer, whatever may be the thick- 
ness of the wire of the spiral, the length of the circuit, the 
diameter of the spiral itself, and the length, thickness, or 
temper of the steel needle. 

If w^e insulate the torpedo, placing on each of its surfaces 
a disc of platinum, upon each of which has been placed a 
piece of paper of the same size^ moistened with a solutioa 



196 



ELECTRIC FISHES. 



Lect. X. 



of iodide of potassium ; and, lastly, close the circuit by ef- 
fecting a communication between the discs by means of a 
platinum wire, we soon find that at each discharge of the 
fish, a reddish yellow spot is formed around the extremity 
of the platinum wire, which touches the piece of paper 
placed on the platinum of the ventral surface. The paper 
on the platinum disc in contact wdth the back of the 
animal, is coloured also, but more feebly. The solution 
which impregnates the paper is, therefore, decomposed by 
the current of the torpedo, and iodine is evolved at the po- 
sitive pole. 

Fig. 13. 




;- ~~-I 'iiillWIIli 
Torpedo placed between the Sole and Cover of an Electrophorug. 

We may also succeed in observing the spark at the mo- 
ment of the discharge. The apparatus employed to effect 
this is very simple : place a very lively torpedo upon a 
large metallic plate, like that of a perfectly insulated elec- 
trophorus, and then put above the fish a disc having an in- 
sulating handle. Each of the two parts of the apparatus 
should be furnished with a metallic wire or rod, to the 
upper extremity of which is attached, by means of gum, a 
piece of gold leaf; the two leaves, consequently, hang 
downwards. We arrange the plates so as to bring the two 
leaves near to each other. By compressing the fish by 
means of the upper plate, and by bringing the two gold 
leaves almost in contact, we frequently see the spark pass 



LeCT. X. PHENOMENA OF THE SHOCK. 197 

from one to the other ; but we can readily understand, that 
the phenomenon is one which is difficult to be seen ; and 
that to succeed in its production, it is necessary to have, at 
the moment of the discharge, the two gold leaves at the 
proper distance for the spark to pass. . 

We succeed more easily if we substitute for the gold 
leaves a steel file, w^hich is connected with one of the discs, 
and on which we rub a metallic wire w^hich communicates 
with the other disc. 

-All the phenomena of the shock of the torpedo must, 
therefore, be attributed to an electrical current. The appa- 
ratus which produces it, consists of two peculiar organs, 
called the electrical organs of the torpedo. Each of the sur- 
faces of these organs possesses an opposite electrical condi- 
tion ; the dorsal surface is positive, the abdominal surface 
negative. The discharge of the animal is voluntary, and 
all external irritation acts upon the electric organ by the 
intervention of the will only. In fact, as the discharge 
would traverse the animaPs own body if there did not exist 
exterior circuits or conductors to receive it, it follows, either 
that the animal will no more produce it, or would immedi- 
ately cease to do so, if it were out of water, or if it were 
either not touched or touched by insulated bodies. It is, 
then, not without reason that nature has placed the animals 
endowed with this property in a liquid conductor. 

The properties of the current of the torpedo resemble those 
of the electric current, properly so called, more than those 
of the discharge of the Leyden phial. 

Let us now examine the discharge of the torpedo as a 
physiological function, and consequently study the influence 
exercised on it by the different parts of the organ itself; 
and by those parts which surround it or which have some 
connexion with it, as well as by the circumstances which 
affect the state of life of the animal. 



198 ELECTRIC FISHES. LeCT. X. 

If we carefully and rapidly remove, from a very lively 
torpedo, one of its electric organs, by separating it from the 
cartilages and integuments which cover and encompass it, 
but leaving uninjured the great nervous trunks which are 
distributed to it, we readily perceive that all its different 
parts, the integuments, cartilages, &c,, have no influence 
upon the discharge. 

Fig. 14. 




Electric organ of the Torpedo. 

Indeed, if we cover the separated organ with prepared 
frogs, and then apply the conductors of the galvanometer 
upon the two surfaces, and irritate the nerves, we observe 
that the frogs contract, and the needle deviates, thus indi- 
cating a current which circulates, as usual, in the galvano- 
meter from the dorsal to the abdominal surface of the organ. 

By proceeding in this way, we observe another very 
curious phenomenon, namely, that the discharge is obtained 
sometimes in one portion of the electric organ, and some- 
times in another. For this purpose it is sufficient to irritate 
separately each of the nerves of the same organ ; and we 
find that all the frogs arranged thereon do not contract, but 
only some of them, viz. those which occupy the point 
where the irritated nerve ramifies. We can obtain these 
discharges for a short period only. Nevertheless, if we 
irritate the nerves by passing an electric current through 
them, the separated organ retains the faculty of giving a 
discharge for a greater length of time. The current which 
traverses the nerve of the electric organ of the torpedo, 
obeys the same laws as those which regulate its action upon 



LeCT. X. PHENOMENA OF THE SHOCK. 199 

muscles. At the moment that the current begins to circu- 
late in the nerve of this organ, it excites the discharge ; if 
it continue to traverse.it, the discharge no longer takes place, 
but we can renew it by interrupting the current. 

Whilst the organ is very fresh, and just separated from 
the living animal, the effects described belong to the direct 
current (that is to say, to a current which proceeds in the 
direction of the ramification of the nerve) as well as to 
the inverse current. But in proportion as the action of the 
current becomes weaker, the phenomena change ; that is 
to say, the direct current excites the discharge only at its 
entrance, and the inverse current only at the moment of its 
interruption. The same result takes place, as we shall here- 
after find, when the current acts on the mixed nerves and 
excites the contraction of the muscles. 

It should also be observed, that in order to excite the 
discharge, the current must be made to act nearer and 
nearer the peripheral extremity of the nerves, in propor- 
tion as the vitality of the separated electric organ grows 
weaker. It also follows, from these facts, that the circula- 
tion of the blood is not absolutely necessary to the electric 
discharge, since the organ preserves this faculty even when 
separated from the animal, when deprived of blood, and 
when the circulation in it no longer takes place. 

The discharge has been found to continue after the pa- 
renchyma of the organ has been pierced and cut in various 
directions, even when the organ had been completely sepa- 
rated from the torpedo ; but it ceases when we coagulate 
the albumen, of which it is in a great part composed, by 
plunging it into boiling water, or by bringing in contact 
with it an acid. 

All these facts prove the influence of the will of the ani- 
mal over the discharge, — an influence which is exercised 
by means of the nerves supplied to the organ. 



200 



ELECTRIC FISHES. 



Lect. X. 



These nerves, then, are neither nerves of sensation nor 
of motion. They possess no other function than that of 

Fig. 15. 

Brain and Cerebral Nerves of the Torpedo. 




I. Cerebrum. 
II. Optic lobes. 

III. Cerebellum. 

IV. Medulla oblongata and electric 

lobes. 



1. Olfactory nerves. 

2. Optic nerves. 

3. Motores Oculorum. 

4. Pathetici. 

5. Trifacial nerves. 

6. Abducentes. 

7. Auditory nerves. 

8. Pneumo-gastric nerves. 



A,B,c,D,E,F,G,H,i,N,x. Different ramifi- 
cations of the trafacial nerve. 

p,Q,R,s,T,u. Ramifications of the pneu- 
mo-gastric nerve. 

L. Branch of the trifacial distributed in 
the electric organ. 

u,T,s. Branches of the pneumo-gastric 
nerve distributed in the electric organ. 

R. Twig, a part of which is distributed 
in the electric organ, 

Q. Lateral and recurrent nerve, fur- 
nished with a ganglion at its base. 

p. Branch distributed to the oesophagus 
and stomach. 

G. Pn. Pineal gland. 



LeCT. X. PHENOMENA OF THE SHOCK. 201 

exciting and bringing into action the organ in which they 
are distributed. 

It was important to ascertain what influence the brain 
exercised over the discharge. For this purpose I exposed 
the brain of a living torpedo, by making a horizontal inci- 
sion of its aponeurotic case, and arranged the prepared frogs 
and the galvanometer upon the body, in order to perceive 
how, and at what moment the discharge took place. 

When we irritate the first lobes of the brain (the olfactory 
lobes) there is no discharge, nor is there if we do the same 
with the optic lobes, and with the cerebellum. These three 
protuberances of the brain may he removed without the tor- 
pedo being deprived of the faculty of giving the discharge. 

A fourth part only of the brain remains, which I have 
named the electric lobe. This can scarcely be touched be- 
fore shocks take place ; and according as we touch the right 
or left side, the corresponding organ gives them. We may 
remove all the other lobes of the brain without affecting the 
electrical function; but if the fourth lobe be torn, the func- 
tion is permanently destroyed, although the others be le^ 
untouched. 

A fact not less extraordinary is, that when even the tor- 
pedo ceases to give the discharges, if we irritate this elec- 
trical lobe, they recommence afresh ; and if we wound it, 
still more violent shocks ensue, which, in some few in- 
stances, I have found to have an inverse direction to that 
which is usual. 

To complete the examination of the phenomena presented 
by the torpedo, I ought to add that this fish ceases to manifest 
its electrical properties when plunged into water at about 
0° centig. [== 32° Fahr.;] but it reacquires them when put 
into water at a temperature of + 15° or 20° centig. [= 59° 
Fahr. or 68°.] We may repeat these alternatives a certain 
number of times upon the same animal. 



202 ELECTRIC FISHES. LeCT. X. 

In water, heated to about + 30° centig. [= 86° Fahr.;] 
the torpedo soon ceases to live, and dies while giving a 
great number of violent discharges. 

When it is frequently irritated while in water, especially 
by compressing it about the eyes, it gives numerous shocks ; 
and then ceases to do so, even though we continue to excite 
it. After a certain period of repose its faculties return. 

Narcotic poisons, strychnia, and morphia, administered 
to these animals in large doses, quickly kill them, after ex- 
citing a great number of violent and rapid discharges. In 
small doses these poisons over-excite the torpedo, and in 
this state the slightest irritation procures shocks. I have 
known a shock produced by giving a blow to the table on 
which the animal was placed. Touched at the tail, it is 
immediately obtained; but if we divide the spinal marrow, 
the parts situated below the section are no longer able to 
give it : it is then a discharge produced by a reflex action 
on the spinal marrow. 

The analogies between muscular contractions and the 
discharge of the torpedo are complete : what destroys, aug- 
ments, and modifies the one, acts equally upon the other. 

Electric Phenomena of the Gymnotus. — Respecting the 
gymnotus, another electric fish found in some of the lakes 
of South America, I have but a few words to say, as the 
animal has been but little studied. I regret I cannot here 
quote a long passage from the work of the celebrated Hum- 
boldt, in which he describes the method of capturing the 
electric eels as adopted by the South American Indians. 
They drive their horses and mules into the muddy lakes 
where these fishes live. These commence the contest by 
giving very violent and very numerous discharges to the 
horses and mules ; and not unfrequently kill them. After a 
long fight, the gymnoti, exhausted by fatigue, float on the 



LecT. X. PHENOMENA OF THE GYMNOTUS. 203 

water, and approaching the margin of the pools, are easily 
captured by the hunters by means of harpoons attached to 
long cords. 

The observations of Humboldt have proved, that the 
discharges of this fish, like those of the torpedo, take place 
without any muscular movement being necessary; and that 
when the brain is removed this phenomenon no longer oc- 
curs, even though the spinal marrow be irritated. The in- 
fluence possessed by the different parts of the brain on the 
electrical phenomena, requires to be more carefully and at- 
tentively studied than it has hitherto been. The mode of 
catching the fish proves, that the discharge is voluntary, 
that the function becomes weakened by being exercised too 
often, and that it is restored by repose. 

Faraday, who made some experiments upon a living 
gymnotus in London, succeeded in obtaining, from the 
discharge of this fish, all the phenomena of the electric 
current; namely, the spark, electro-chemical decomposition, 
the action upon the magnetic needle^ &c. Furthermore, 
he compared the shock given by this fish to that of a battery 
of Leyden jars charged to its highest degree; and he 
concluded, from his experiments, that a single medium 
discharge of this animal, is equal to that of a battery of 
fifteen jars, containing 3500 English square inches, charged 
to its highest degree. It cannot, therefore, be a matter of 
surprise that a horse sinks under a number of successive 
discharges given by the gymnotus. 

The most important result which Faraday obtained, was 
that respecting the direction of the discharge. The cephalic 
extremity is the positive, and the opposite extremity is the 
negative pole ; so that the current circulates in the galvano- 
meter from the head towards the tail of the animal. This 
arrangement explains the stratagem employed by the ani- 
mal when giving the shock for the purpose of killing a fish ; 



204 ELECTRIC FISHES. LeCT. X. 

it coils itself so that its victim is enclosed in the concavity 
formed by its body. 

I have myself recently made some experiments upon a 
gymnotus, which had lived for several months in the palace 
of the King at Naples ; and have verified all the facts ob- 
served by Faraday. The only important and new result 
which I obtained was, that the fish possessed the power of 
discharging voluntarily either the whole or only a part of 
its organ. Fresh researches, however, are necessary to 
substantiate fully this fact. We know nothing of the other 
electrical fishes ; and I can, therefore, only mention their 
names to you. 

What does the organ of the electrical fishes consist of? 
What electrical apparatus is analogous to this organ ? It is 
very difficult to answer these questions satisfactorily. The 
electric organ of the torpedo is composed of from 400 to 
500 prismatic masses, comparable to grains of rice, placed 
side by side, each of which is composed of superimposed 
vesicles. From this general arrangement, the entire organ 
resembles a honey-comb. Each of the component prisms 
present a certain number of diaphragms, which divide it 
perpendicularly to its axis, and which in fact are nothing 
more than the aponeurotic walls of the neighbouring vesi- 
cular masses. Nervous ramifications, consisting entirely of 
primitive nerve fibres, are distributed over these walls or 
diaphragms. Savi, Robin, and Wagner, have studied this 
structure. 

The great resemblance, or, to speak more accurately, 
the identity of structure of all these vesicles, leads us to 
assume that they are the true elementary organ of the elec- 
tric apparatus : the truth of this hypothesis is also demon- 
strated by the identity of their composition ; for all are 
filled with the same dense liquid, composed of about -^^ of 
water and iV of albumen, with a little common salt. Ex- 



LeCT. X. PHENOMENA OF THE GYMNOTUS. 205 

periment proves directly, that each of these vesicles forms 
the elementary organ of the electric apparatus. I have 
removed from a living torpedo a portion of one of its prisms, 
about the size of the head of a large pin, and I placed it 
in contact with the nerve of the galvanoscopic frog, and 
frequently observed contractions produced in the frog, on 
pricking the fragment of the prism with a piece of glass, 
or any other pointed body. Now, if you consider that 
each of the prisms is composed of a very large number of 
vesicles or elementary organs, that Hunter counted 470 
prisms in each organ of the torpedo, you will understand 
that the discharge, being proportional to the number of 
vesicles, must necessarily be very strong. 

The electric organ, then, is a true multiplying appa- 
ratus. 

Volta supposed that it was "a pile which the animal itself 
rendered active by compressing its organ, and thus esta- 
blishing the contacts between the latter and the skin. But 
the experiments which we have described to you, in no 
way confirm this hypothesis. It has been lately stated, 
that the electric organ was analogous to the electro-mag- 
netic coil, and that the discharge was a phenomenon of ex- 
trn-current or of induction. 

If we assume, what microscopic observation proves that 
in each vesicle there exists a nervous filament, which here 
divides, it is difficult to discover the analogy between the 
electric apparatus of the torpedo and an electro-dynamic 
coil. 

Let us advance an hypothesis, which we shall hereafter 
find to be supported by facts, or, at least, by powerful ana- 
logies. 

Suppose, that every time the nervous irritation reaches 
one of the elementary vesicles of the organ of the torpedo, 
that the two electricities separate. Heat, which acts on 



206 



ELECTRIC FISHES. 



Lect. X. 



the tourmaline, and on some crystallized metals, separates 
the two electricities : chemical action operates in the same 
way ; as do also the mechanical actions, friction, and pres- 
sure. Suppose, that nervous irritation acts in this way on 
the vesicle of the electric organ. The identity of struc. 
ture, and the arrangement of each of the vesicles, is such 
that each of the prisms becomes a pile, but only for the 
infinitely small period of the duration of the irritation ; and, 
consequently, the entire organ will be a multiplying appa- 
ratus, which will remain charged only for an instant, since 
it is surrounded by conducting bodies. The discharge will 
take place partly outside the surrounding medium and 



Fig. 1 6. 



Dorsal surface (positive.) 




Cephalitic extremity (positive.) 




Ventral surface (neorative) 
Electric Organ of the Torpedo. 



Caudal extremity (negative.) 
Electric Organ of the Gymnotus. 

partly in the interior of the organ ; but so much more out- 
side as the medium will be a better conductor than the in- 
terior of the organ. Yet it may be remembered that we 
have shown, by experiment, that this discharge really takes 
place internally. 



Lect. X. siLURus. 207 

It results from this hypothesis, that the opposite electri- 
cal conditions ought always to be found at the long extre- 
mity of the prisms ; and that their intensity should be pro- 
portional to the length of these prisms; that is, to the num- 
ber of cells of which each is composed. It is important 
to remark, that these hypotheses are confirmed by experi- 
ment. 

In fact, the relative position of the poles in the gymno- 
tus, correspond to those of the poles of the torpedo as re- 
gards the extremity of the prisms. In the first of these 
fishes, the prisms are extended along the axis of the body 
of the animal, that is, from the head towards the tail, or 
vice versa ; in the second, on the contrary, the prisms have 
their extremities in contact with the back and the belly. 
Hence, then, in the gymnotus, the poles are the head and 
the tail, and in the torpedo we find them at the back and 
the belly. 

Silurus. — It remains for us to examine the direction of 
the current of the silurus ; if we are to judge from the 
structure only of the organ in this fish, we must conclude 
that the two poles are, in the gymnotus, at the head and 
the tail. 

The intensity of the electric discharges, is the strongest 
at the points of the organ nearest to the mesial line ; there, 
also, the height of the prisms, and the number of nervous 
filaments are the greatest. 

Microscopic anatomy may also render a great service to 
physics, by studying the electric organ of fishes, and parti- 
cularly by establishing exactly the distribution of the nervous 
filaments in the elementary organ or cell. This cell ap- 
pears to be largest in the silurus, and, therefore, it is in this 
fish that the structure should be studied. 

What happens in the electric organ, is certainly analo- 
gous to electric induction :. the constancy of the direction 



208 ELECTRIC FISHES. LeCT. X. 

of the discharge, indicates a determinate direction in the 
action of the nervous force ; and there appears some 
foundation for this supposition, when we consider that the 
excitation of the fourth lobe, and of the electrical nerves 
of the torpedo has no other effect than that of producing the 
discharge. 

Proper Current of the Frog. — Lastly, I must mention to 
you another phenomenon of animal electricity which has 
hitherto offered, by its speciality, some analogy to those we 
have observed in the electric fishes. I refer now to the 
current proper to the frog. 

Galvani discovered, and all philosophers after him have 
observed, that a frog, prepared according to his usual me- 
thod, contracts when we bring the lumbar nerves in contact 
with the muscles of the thigh or leg. Nobili was the first 
to study this phenomenon by the aid of the galvanometer. 
Here is his fundamental experiment : a frog prepared in 
the usual manner is placed between two small glasses 
containing distilled water, in such a manner that on one side 
the lumbar nerves, on the other, the legs, are immersed in 
the liquid. Matters being thus arranged, the circuit is 
closed by plunging into the two glasses the two platinum 
extremities of a galvanometer. Observe the needle; it 
deviates, and from 0° where it was, it reaches 5°, 10°, 
and even 15°. You see that the direction of deviation in- 
dicates a current circulating in the frog from the legs to the 
nerve ; that is to say, from the legs to the upper part of the 
animal. 

The signs of the current are augmented in intensity if, 
in place of using a single frog, I form a pile with a number 
of them. 

This arrangement is very easily understood : I employ 
the varnished tray before spoken of, -when treating of the 
muscular current. I place on it some frogs, prepared in 



LeCT. X. PROPER CURRENT OF THE FROG. 209 

such a way that the nerves of the first animal touch the 
legs of the second, and the nerves of the second the legs 
of the third, and so on. I thus have a pile, one extremity 
of which is formed by the legs, and the other by the nerves. 
I plunge the two poles of this pile into two cavities of the 
tray, which contain either a very weak saline solution or 
distilled water. Into these I also put the two extremities 
of the wires of the galvanometer. You see that the needle 
deviates, and indicates precisely, as in the experiment of 
Nobili, the existence of a very energetic current which cir- 
culates from the legs to the nerves in each of the frogs 
which form the pile. I have repeated and varied in a thou- 
sand different ways this experiment, which has enabled me 
to ascertain that the variation of the needle is proportional 
to the number of frogs composing the pile ; that it is more 
considerable w^hen we employ an alkaline or saline solu- 
tion, or, better still, an acid solution, than when we em- 
ploy distilled water ; that, whatever be the liquid employed, 
the direction of the current is constant, and circulates al- 
ways in the pile, from the feet to the upper part of the frog. 

On repeating these experiments, you will observe that at 
the moment when the galvanometer indicates the presence 
and the direction of the current, the frogs contract. 

The contractions are analogous to those observed by 
Galvani ; they take place whenever we complete the cir- 
cuit with a conducting body, as, for example, with a wick 
of cotton, or a piece of paper moistened with water, or any 
conducting liquid, provided that the arrangement be such that 
the conducting substance communicates on one side with 
the nerves, and on the other with the muscles of the ani- 
mal. These contractions are also observed at the moment 
when we interrupt the circuit. 

This current was at first called the current of the frog ; 
but for this name I afterwards substituted another, that of 
14 



210 ELECTRIC FISHES. LeCT. X. 

the proper current of the frog, because, until recently it 
was in the frog alone that we could recognise its existence. 

I have endeavoured to ascertain what part of the inferior 
extremity of this animal was necessary to the production 
of the current, or what influence the different parts of the 
limb had upon it. I will show you an experiment which 
will solve these questions. 

Here are two piles opposed to each other, each formed 
of the same number of elements. One of them is com- 
posed of six frogs, prepared according to the method of 
Galvani, the other of six legs only, the thighs and spinal 
nerves being removed. The six elements of the first touch 
the six of the other ; but their arrangement is inverse, so 
that at the point of the junction there come in contact, on 
one side, nerves, and on the other, the upper end of the 
leg. Thus the two piles are opposed : I put the wires 
of a galvanometer in connexion with the two extremities 
of the two piles, and I obtain no signs of a differential 
current. 

The proper current of the frog has, then, for the organic 
element, the leg only. 

Recently, by studying more attentively the proper cur- 
rent, I have satisfied myself that it is a phenomenon which 
appertains to all animals. Here is the enumeration of the 
fact : in every muscle endowed with life, in which the ten- 
dinous extremities are not equally disposed, there exists 
a current directed from the tendon to the muscle, in the 
interior of the latter. All animals have some muscles, in 
which one tendinous extremity is narrower than the other ; 
and which, at one part, forms a kind of cord, and at the 
other, becomes broader and riband-like. In the frog, and 
many other animals, the gastrocnemius has this character: 
in birds, the pectoral muscle presents this arrangement. 
When we form a pile with these muscles, we find that a 



LeCT. X. ITS ORIGIN. 211 

current circulates in the muscle, from the tendinous ex- 
tremity to the muscular surface. 

In arranging this pile, we must carefully avoid exposing 
the internal part of the muscle, and we must especially 
place one element in contact with another, in such a man- 
ner that the tendinous extremity touches the surface of the 
muscle, and never its interior : indeed, the latter ought to 
be as far as possible from the tendon. Without this pre- 
caution there will be, in the circuit, the muscular current 
which, being directed from the interior to the surface, would 
have a direction precisely the reverse of that of the proper 
current. The existence of the proper current of the frog, 
in all animals in the way described, was found at the same 
time by M. Cima, by M. Boy-Raymond, at Berlin, and by 
myself. 

Having thus ascertained the conditions on which the 
proper current depends, I think that I may generalize its 
origin, and connect it with the muscular current. This 
community of origin is principally demonstrated by the 
identity of action which the different circumstances that 
modify the organism and life of animals, exercise upon the 
muscular current. In fact, whether the current be muscular 
or proper, the action exercised on it by heat, narcotics, 
sulphuretted hydrogen, and the degree of integrity of the 
nervous system is the same. 

Anatomists, and especially Bowman, have lately demon- 
strated, that the elementary muscular fibres are immediately 
continuous w^ith the tendinous fibres, and that the sarco- 
lemma which invests the muscle, ceases abruptly where the 
tendon begins. We may, then, with some probability, con- 
sider the tendon as being in the same electric condition as 
the interior of the muscle ; and, therefore, when we form, 
by means of a good conductor, a circuit or communication 
between the tendon and the sarcolemma, we put into cir- 
culation a portion of the muscular current. 



212 GRAVITY, LIGHT, AND CALORIC. LeCT. XI. 



LECTURE XL 



PHYSIOLOGICAL ACTION OF GRAVITY, LIGHT, AND CALORIC. 

Argument. — 1 . 4^ction of Gravity. Experiments of Hunter and Knight on 
the influence of gravity on the germination of seeds. 

2. Action of Light. Influence of light on the development, and on the 
colours, of animals. Influence of lighten the respiration of plants; 
illustrative fact observed in the process of the Daguerreotype. Influence 
of light on the germination of seeds, and on the direction of the roots of 
plants. 

3. Action of Caloric. A certain degree of heat is essential to vitality. 
Actions of contact take place only at certain temperatures; these pro- 
bably have some agency in the phenomena of living beings, especially 
in fecundation. Influence of temperature on the life of frogs. Relation 
between respiration and temperature. Capability of man and other 
mammals to bear extremes of heat and cold. Refrigerating process of 
the animal body. 

We have hitherto spoken of the development of heat, 
electricity, and light, in organized living beings; but we 
must now study their action upon these bodies. 

Action of Gravity, — I think it unnecessary to say that, in 
speaking of the action of gravity upon living beings, I do 
not mean to notice that which is exercised upon bodies 
generally; which makes them, when left to themselves, fall 
to the earth, and which causes them to press on the surface 
which supports them, and to maintain themselves in equili- 
brio when their centre of gravity is supported or sus- 
pended^ 



LeCT. XL ACTION OF GRAVITY. 213 

But I wish to speak of a peculiar phenomenon which 
presents itself in the development of vegetables, and in 
which it is impossible not to recognise the effect of 
gravity. 

In general, the seeds of all vegetables germinate and 
shoot, by manifesting the tendency which their roots have 
to descend, and their stems to ascend. Experience proves 
that the opposite direction which these parts of the plant 
take, is owing neither to the moisture of the soil, nor to the 
action of light or of atmospheric air. The roots continue 
to descend, and the stems to ascend, even when their 
natural position is inverted ; that is to say, when the latter 
is placed in contact with the earth, and the former is sub- 
mitted to the action of light. We are indebted to Knight 
for some ingenious experiments, which, if they do not 
entirely clear up this subject, at least have demonstrated 
the existence of one of the causes which preside over this 
phenomenon. 

Hunter was the first who observed, that if a barrel filled 
with earth, in the centre of which were some beans, be 
rotated, for several days, horizontally, the roots pointed in 
a direction parallel to the axis of rotation. 

Knight fixed some garden beans on the circumference of 
a wheel, supplied them with moisture, and kept the wheel 
revolving for a considerable time. He found, that when 
the wheel was vertica], the radicles or roots of the young 
plants pointed towards the circumference, and the stems 
towards the centre of the wheel ; but when the wheel was 
horizontal, the roots and the stems pointed obliquely, the 
roots being always directed towards the circumference. 

By considering Knight's experiment in connexion with 
the first one quoted, and which demonstrates that the direc- 
tion of stems and roots is under the influence of gravity, it 
follows, that in the second experiment these point obliquely, 



214 GRAVITY, LIGHT, AND CALORIC. LeCT. XI. 

in order to place themselves between the horizontal position 
which tends to make them acquire the centrifugal force, 
and the vertical, which is natural to them, and which they 
take in their ordinary conditions. 

It is evident that, in order to find an explanation of the 
facts discovered by Hunter and Knight, we must admit : — 

1st. A more or less liquid condition of the new parts of 
the young plant; 

2dly. A different density in the different parts of the 
latter; and, 

3dly, That the denser parts of the new plant are directed, 
at least in the first stage of germination, towards the roots. 

From these conclusions it follows that, in the case of the 
vertical wheel, the parts of the young plant, being submitted 
to the action of the centrifugal force only, developed them- 
selves by having their densest parts, namely, their roots, 
at the circumference ; while, in the case of the horizontal 
wheel, they took an intermediate position, between that 
which the centrifugal force impressed on them, and that 
which they would have acquired if they had been under the 
influence of gravity only. 

Dutrochet, without denying the influence of gravity upon 
the ordinary direction of roots and stems, admits, neverthe- 
less, a second cause for this phenomenon. It may depend 
on the unequal development of the cellular system of the 
roots and stems, and on the different turgescence which en- 
dosmose produces in the cells of this system. 

Miction of Light on Animals. — Let us now speak of 
light. 

We know nothing, or scarcely any thing, respecting the 
action which this agent exercises upon animals. Edwards 
has proved, that the ova of the frog are more rapidly deve- 
loped in the sun than in darkness ; and also, that tadpoles 



LeCT. IX. ACTION OF LIGHT ON VEGETABLES. 215 

more quickly and completely changed into frogs under the 
same condition. 

The colours of animals are brighter in proportion to the 
intensity of the light to which they are submitted. It has 
been asserted, that the quantity of carbonic acid exhaled by 
the skin of an animal, is augmented by the action of the 
solar rays. But not knowing which of the rays of the sun 
produce these effects, we do not know whether these effects 
are due to the chemical action of the rays, however proba- 
ble this may otherwise appear. 

Action of Light on Vegetables. — The action of light on 
vegetables, although still obscure, is better known with re- 
spect to its laws, and exercises a great influence upon the 
life of these beings. It has been proved, that the respira- 
tion of a plant, namely the decomposition of carbonic acid 
effected by the green parts, the fixation of carbon, and the 
exhalation of oxygen, take place only under the influence of 
solar light : in darkness the plant, on the contrary, absorbs 
oxygen and emits carbonic acid. In light, vegetables be- 
come coloured, and their tissues harden ; whilst, in dark- 
ness, they lose their colours, and their stems elongate and 
become soft. A very vivid artificial light acts like that of 
the sun, although in a much feebler degree. We possess 
only a single fact capable of explaining this singular action 
of the sun. It has been observed, in executing images 
with the Daguerreotype, that the green parts of vegetables, 
and, in general, all green bodies, are not represented, being 
the contrary to what takes place with objects of other co- 
lours. Now, since it is well established that, in the forma- 
tion of images, by the well-known process of Daguerre, 
these are owing to the influence of the chemical rays of solar 
light, we are compelled to assume that the green parts are not 
produced because they entirely absorb the rays. A very 



216 GRAVITY, LIGHT, AND CALORIC. LecT. XI. 

natural conclusion to draw from this fact is, that the production 
of the green matter in vegetables, and the extraordinary pro- 
perty with which this substance is endowed, of decomposing 
carbonic acid under the influence of light, of appropriating 
to itself the carbon and of exhaling the oxygen, take place 
under the chemical action of the solar rays. Nevertheless, 
it follows from some of Draper's experiments, that the lu- 
minous rays, properly so called^ those which act more espe- 
cially on the retina, viz. the yellow rays, are those under 
whose influence principally the green matter of vegetables 
decomposes carbonic acid. With respect to the absorption 
of oxygen and the exhalation of carbonic acid in darkness, 
it is admitted, that these are effected independently of the 
condition of life. 

You perceive, by the little w^hich I have been enabled to 
state to you respecting this very important subject, how 
very limited our knowledge is respecting it. What is 
really the immediate chemical principle which acts thus in 
plants, and which is capable of accomplishing a chemical 
action, whose intensity has no parallel in the most energetic 
ordinary chemical affinities ? What share does the organism 
take in this action ? 

In a balloon, filled with v^ater acidulated with carbonic 
acid, I exposed to the light some leaves which had under- 
gone a very strong trituration, and I obtained no trace of 
oxygen, whilst, in another similar apparatus, in which the 
leaves w^ere uninjured, I soon discovered its presence. I 
may also add, that there is a great number of green vege- 
table parts containing a substance analogous to that of the 
leaves, and having no action upon carbonic acid in solar 
light. It is very desirable that these experiments should 
be extended and varied, in order to establish the influence 
of organization on the respiration of plants. 



LeCT. XL ACTION OF LIGHT ON VEGETABLES. 217 

The influence of the luminous rays on germination has 
been of late spoken of. Some observers have asserted, that 
the violet, or chemical rays, promote it ; whilst others main- 
tain an opposite opinion. This contradiction is a fresh proof 
of the necessity of having recourse to more exact experi- 
ments. It is not difficult to discover the source of the dif- 
ferent results obtained by experimentalists, since they have 
not employed the simple rays of the solar spectrum ; but the 
coloured rays obtained by the passage of solar light through 
glasses of different colours. Now, in general, a solar ray 
which traverses coloured glass, is not deprived of all the 
rays w^hich possess colours different to that presented by 
itself. 

A curious effect of light upon vegetables is seen in the 
tendency which certain roots have to avoid it ; and, on the 
contrary, which others evince to seek it. The roots of many 
plants belonging to the family Crucifera, do the former ; 
those of Allium cepa^ the latter. According to Dutrochet, 
the intimate structure of the cortex of roots, is different ac- 
cording as they seek or avoid the light ; and from this dif- 
ference results the tendency which they evince to direct 
themselves one way or the other. Generally, in the barks 
of young plants, the utricles are largest in the median 
layers of its thickness, and decrease in size as they approach 
both towards the interior and the surface ; but in some 
cases this decrease is less towards the outer layers ; while 
in others, it is less towards the inner ones. Under the in- 
fluence of solar light and heat, the plant transpires and the 
utricles yield up the water they contain. It follow^s, there- 
fore, that the roots direct themselves towards the light, 
when the structure of the internal layer of the bark is 
denser than that of the external ; and the reverse effect 
takes place when the external layers possess a greater 
density. 



218 GRAVITY, LIGHT, AND CALORIC. LeCT. XI. 

Action of Caloric on organized Beings. — I have, in the 
last place, to notice the influence which heat exercises over 
living organized beings. 

A suitable temperature is a condition essential to life. 
The possibility of living, is indeed comprised within cer- 
tain limits of temperature, beyond which there are no 
examples of the development and preservation either of 
animals or vegetables. With respect to the general mode 
of action of heat, it will be sufficient to say, that all the 
physico-chemical phenomena of living bodies can be pro- 
duced within those limits of temperature, which are also 
the limits of vegetable and animal life. 

We now know, that the different actions of contact take 
place only at a certain temperature, and we must not forget 
that these actions intervene in a great number of the phe- 
nomena of living beings ; and the little which we know of 
these actions gives us an imperfect notion only of all the 
uses which yet remain to be made of them. 

The fecundation and germination of plants occur at a 
certain temperature only, and the actions of contact play 
an important part in these mysterious phenomena. 

Independently of this general mode of action of heat on 
living beings, we must more particularly study its influence 
upo^ animals. 

From that classical work, entitled. On the Influence of 
Physical Agents upon Life^ I shall draw the most important 
discoveries that have been made on this subject, and to 
which I shall confine my notice. 

Edwards, when studying the life of frogs, in river water 
at different temperatures, saw that at 0° centig. [ = 32° 
Fahr.] these animals lived eight hours ; at a temperature 
of 4- 10° [ = 50° Fahr.] they lived only six hours ; at + 
16° centig. [ = 60°-8 Fahr.] two hours ; at -f 22° centig. 
[ = 71°*6 Fahr.] from seventy to thirty-five minutes ; at 



LeCT. XL ACTION OF CALORIC. . 219 

-1-32° [ = 89°-6 Fahr.] from thirty to twelve minutes : 
and at + 42° centig. [ = 107°'6 Fahr.] death was instanta- 
neous. 

The very great influence exercised by slight variations of 
temperature upon the life of frogs, cannot be ascribed to 
the different quantity of air dissolved by the water at these 
different temperatures. We know, indeed, that this varies 
very little in different seasons, and yet w^e have seen that 
the differences of temperature of the year produce very 
marked effects upon the life of frogs immersed in water. 

Edwards found that the quantity of air which these ani- 
mals respire is greater in proportion to the higher tempera- 
ture of the medium in which they live ; so that the quantity 
which is usually dissolved in water, even when constantly 
renewed, is not sufficient for them if the temperature be at 
all elevated. Frogs, then, only live in water at very low 
temperatures ; except they can come to the surface, and 
respire atmospheric air. We observe, with fish, analogous 
phenomena. Immersed in a certain quantity of water con- 
taining air in solution, but which is not in contact with the 
atmosphere, the duration of their life is longer in proportion 
as the temperature of the water is lower. 

We have already described an experiment of this kind, 
made on a torpedo contained in water at + 28° centig. 
[ = 82°'4 Fahr. ;] it soon died, in giving a series of strong 
shocks; and, on the contrary, lived a long time in cold 
water, giving few and feeble discharges. 

The relation found between the respiration and the tem- 
perature of the medium, in which the animals, we are now 
speaking of, live, is a further proof of the chemical nature 
of this function. 

Man, and mammals in general, are able to support a 
temperature much higher than that which is proper to them. 
The observation of Tillet and Duhamel is well known. 



220 GRAVITY, LIGHT AND CALORIC. LeCT. XI. 

They saw a young girl remain for twelve minutes in an 
oven, the temperature of which was 128° centig. [ = 
262°-4 Fahr. ]. Delaroche and Berger introduced rabbits, 
cats, and several other vertebrated animals, into an oven 
heated to from + 56° to + 65° centig. [ = l32°-8 to 149° 
Fahr.]. The animals died at the expiration of some 
minutes. These observers concluded, from a great number 
of experiments, that vertebrated animals, when exposed to 
a dry atmosphere heated to + 45° centig. [ = 113° Fahr.,] 
are near the extreme limit of temperature in which they are 
capable of living. It appears, then, that man alone is en- 
dowed with the faculty of supporting a higher temperature ; 
indeed, besides the instance already mentioned, there exists 
others, of the truth of which no doubt exists. 

Dobson tells us of a young man who remained for 
twenty minutes in an oven heated to + 98-88° centig. 
[ = 210° Fahr. ;] his pulse, which was usually sixty-five, 
was, when he came out, a hundred and sixty-four. Berger 
supported, for seven minutes, an atmosphere at -f 109° 
centig. [ = 228°-2 Fahr.,] and Blagden was enclosed ia 
one heated to + 127° centig. [ = 260°-6 Fahr.]. 

But it is different if the heated air be saturated with 
aqueous vapour. Berger could remain only twelve minutes 
in a vapour bath whose temperature was raised from -f 
45°-25 to 53°-75 centig. [ = ll3°-45 to 128°-75 Fahr.]. 
The temperature which a man can support when in heated 
water, is still less than that which he is capable of enduring 
in a vapour bath. We shall soon see what are the causes 
of this difference. 

It was important to ascertain the variations in the tem- 
perature of animals exposed to different degrees of heat. 
If we limit ourselves to the ordinary variations of tempera- 
ture of climates and seasons, the heat of the human body 
is not perceptibly modified. The numerous experiments of 



LeCT. XL ACTION OF CALORIC. 221 

Dr. John Davy on this point, give only very slight differ- 
ences. Franklin was the first to observe, that the tempera- 
ture of his body wSs -\- 35°-55 centig. [ = 96° Fahr.], 
whilst the air was at + 37°-77 centig. [ = 100° Fahr.]. 
The conclusion drawn from this fact was, that warm-blooded 
animals had the faculty of remaining in a degree of heat 
below that of the medium in which they exist. Neverthe- 
less, it was necessary to ascertain whether, if placed in a 
temperature much higher than that which is natural to man, 
the temperature of his body didnot undergo some variations. 
Delaroche and Berger found an increase of 5° centig. [ =s 
9° Fahr.] in the temperature of one of them, who had re- 
mained for eight minutes in a chamber heated to -f 86° 
centig. [ = l86°-8 Fahr.]. The same experimentalists 
have repeated their trials upon mammals and birds, and 
ascertained that the exposure of these animals to a hot and 
dry air produced an elevation in their temperature, but that 
it cannot exceed 7° or 8° centig. [ = 12°-6 to 14°-4 Fahr.] 
without causing death. 

An elementary knowledge of physics suffices to ex- 
plain the effects of the exterior temperature on the heat of 
animals. The formation of aqueous vapour, which con- 
stantly escapes by the skin of an animal, is a permanent 
cause of refrigeration for it. This fact explains why in hot 
and dry air the temperature of the animal is not so high 
as when the air is loaded with vapour. 

There exists, then, in the animal, a constant source of 
heat, and a constant cause of refrigeration, and an almost in- 
variable temperature is maintained, notwithstandingthe vari- 
ations which take place in the exterior media, whether 
colder or hotter than itself, since the cause of cooling is 
more energetic in proportion as the temperature is higher,, 
and vice versa. 

Edwards tried a great many experiments with the view 



222 GRAVITY, LIGHT, AND CALORIC. LecT. XL 

of determining whether there existed any difference in the 
refrigeration going on in an animal, by its immersion in an 
atmosphere colder than its own, acc(frding as this was 
moist or dry ; and the conclusion was, that it was the same 
in both cases. If we consider that in moist air heat ought 
to be diffused more easily than in dry air, we may explain 
the result which Edwards obtained, by saying that the re- 
frigeration produced by the more considerable evaporation 
which takes place in dry air, can be compensated for by 
the loss of heat effected by contact with moist air. But 
there is, on the contrary, a very considerable difference 
in the cooling of an animal, according as the atmosphere 
is calm or agitated. When it is tranquil, and at a tempe- 
rature below that of our own body, we lose heat by evapo- 
ration, by contact with air, and by radiation. The pre- 
sence and nature of the gas and its agitation, have no per- 
ceptible influence on the loss by radiation ; but this is 
not the case with the loss occasioned by evaporation or 
by contact with the air, which is considerably augmented 
by the motion of the air. These results are evidently the 
consequence of the physical laws of the cooling of bodies 
in the air, and of the effects of evaporation. Parry re- 
lates, that he has often supported a temperature of — 17°'77 
centig. [=0° Fahr.,] without suffering therefrom, when 
the atmosphere was calm ; whilst a cold of — 6^-66 cen- 
tig. [= 20° Fahr.] was very annoying, when accompanied 
by even a slight wind. And the surgeon, who accompanied 
Captain Parry in his celebrated expedition, relates, that in 
a calm air, the sensation produced by a temperature of 
46°-ll centig. [== — 51° Fahr.] might be compared to that 
which they experienced at — 17°-77 centig. [= 0° Fahr.] 
with a breeze. It follows from this observation, that a 
certain agitation of the air will produce a sensation of cold 



LeCT. XI. ACTION OF CALORIC. 223 

equivalent to the effect of a fall of 29°*6 of the centigrade 
scale [=53°-28ofFahr.]* 

* Thefc is, I suspect, a typographical error in one, at least, of the 
temperatures referred to. Captain Parry {Journal of a Voyage for the 
Discovery of a North-West Passage, 1821, p. 145,) alluding to a tempe- 
rature of — 55° Fahr. [= 48°-3 centig.] observes that "not the slightest 
inconvenience was suffered, from exposuse to the open air, by a person 
well clothed, as long as the weather was perfectly calm ; but in walking 
against a very light air of wind, a smarting sensation was experienced all 
over the face, accompanied by a pain in the middle of the forehead, which 
soon became rather severe." Is this the passage to which Matteucci re- 
fers ?— J. P. 



224 ELECTRIC CURRENT. LeCT. XII. XIII. 



LECTURES XII. and XIII. 

PHYSIOLOGICAL ACTION OF THE ELECTRIC CURRENT. 

Argdment. — Effects of statistical electricity on living beings. Galvani's 
hypothesis of animal electricity. Convulsions produced in living and 
recently killed animals by the electric current. 

Action of direct and inverse currents on the sciatic nerve of a frog. Two 
periods in the action of the current. Rejlex movements caused by the 
current. Effects of the current on the nerves of recently killed ani- 
mals. 

Action of the current on muscular Jibre, The contractility of the fibre is 
inherent. 

Voltaic alternatives. Contractions renewed in the muscles of a frog by 
reversing the current. 

Action of the current on poisoned animals. Further evidence that the 
muscular fibre contracts under the influence of the current, indepen- 
dently of the nerve. 

Action of the current on a nerve to which a ligature has been applied. 

Opposite effects of the direct and inverse current. Brequet's apparatus 
for measuring the contraction caused by the current. General conc'u. 
sions. Effect of repose on a nerve which has been submitted to the 
electric current. 

Theory of the action of the electric current on the nerves. 

Effects of the electric current on the brain, on the columns of the spinal 
marrow, on the roots of the spinal nerves, on the nerves of sensation, and 
on the ganglionic nerves. 

Effects of the interrupted current on the excitability of nerves ; it more 
speedily exhausts the nerves than the continued current. Masson's ap- 
paratus. 

Therapeutical uses of the electric current. Employment of it in paralysis, 
and in tetanus ; rules for its application. It is useless in the treat- 
ment of urinary calculi and cataract. Proposed employment of it in 
aneurism. 

In this lecture I shall examine the physiological action 
of electricity. 



LeCT. XII. XIII. STATICAL ELECTRICITY. 225 

Effects of Statical Electricity. — I need not dwell long 
on the effects of statical electricity on animals and vegeta- 
bles; for though in old works on physics we find some 
strange and wonderful effects attributed to it, more accurate 
observations have completely disproved these statements. 
An animal or a plant, insulated and electrified by means of 
the electric machine, has hitherto presented no phenomenon 
peculiar to them, or different from those offered by inorganic 
bodies when submitted to the same influence. But this is 
not the case with respect to the action of the electrical dis- 
charge on animals. 

Effects of Dynamical Electricity. — This subject is of the 
highest importance, and I am anxious to make you acquaint- 
ed with every particular regarding it. 

In a memoir, found among the manuscripts of Galvani, 
and bearing this title, in his own handwriting. Experiments 
on the Electricity of the Metals^ dated 20th September, 
1786, a fact is mentioned which certainly has had as much 
influence on the advancement of science, as any of the 
discoveries of Galileo and Newton. It is, that contractions 
are excited in a frog, recently killed and prepared according 
to the usual method of Galvani, when we touch its muscles 
and nerves with an arc composed of two different metals. 

I shall not stop to explain to you how Galvani interpre- 
ted these facts, by assuming the existence of an animal 
electricity which the metallic arc merely discharged. After 
Volta had demonstrated, by the condensing electrometer, 
that the two electricities were separated by the effect of the 
contact of two metals, the idea of Galvani's animal elec- 
tricity was abandoned, and it was generally supposed that 
the contractions observed in the frog, were simply the effects 
of the passage through the nerves, of electricity developed 
by the two metals. The two last lectures have taught you 
in what animal electricity really consists; and you must be 
15 



226 ELECTRIC CURRENT. LeCT. XII. XIII. 

convinced that Galvani's assumption was not erroneous, 
since a great number of facts discovered by him are cer- 
tainly due to the electricity developed in, and proper to, 
animals. 

The contractions excited in the frog, or in any other 
animal living or recently killed, when one of its nerves is 
traversed by the electric current, are quite independent of 
all animal electricity. It is by the examination of this first 
fact, that we shall commence our study of the action of 
electricity upon animals. 

For some years after the discoveries of Galvani and 
Volta, every journal and every work teemed with particu- 
lars relating to them. The convulsions and the leaps 
observed in recently killed animals that are submitted to a 
sufficiently powerful electric current, at first gave hopes of 
the possibility of the restoration of life. This illusion, of 
course, soon disappeared, and science withdrew within the 
proper limits of its domains. Valli, Lehot, Humboldt, 
Aldini, Marianini, and Nobili, have subsequently studied 
the physiological action of the electric current. 

As I cannot possibly here relate all their experiments, 
I must limit myself to a notice of those matters which, in 
the present state of science, appear to be best established. 

Effects of the Current on the Sciatic JYerves, — In this 
rabbit, which you observe is firmly fixed by its four paws 
to the table, I expose the sciatic nerve in both thighs. I 
separate it as much as possible from the surrounding parts, 
then wipe it with some unsized paper, and introduce be- 
neath it a band of gummed taflTeta to insulate it completely 
from the neighbouring tissues. You perceive the effect 
produced when I transmit the current from a pile of ten 
elements along the nerve, by applying the two conductors 
at a little distance from each other, in such a manner that 
its direction is^ftom the centr;a]j)art of the nervous system 



LeCT. XII. XIII. EFFECTS ON SCIATIC NERVES. 22T 

to the periphery of the nerve (that is, in the direction of the 
ramifications of the nerve.) At the moment when I close 
the circuit, all the muscles of the thigh contract, the animal 
utters loud cries, its back becomes forcibly bent, and its 
ears are agitated. 

These phenomena recur when? I change the respective 
position of the electrodes ; that i&, when I cause the current 
to pass in the reverse way to that which it previously did, 
and direct it from the periphery to the nervous centres. 

The effects which you observed at the moment when I 
closed the circuit, are repeated when I open it, by inter- 
rupting the communication of the conductors with the nerve, 
both when the current is in the first direction [direct cur- 
rent,) and when it is in the second, or opposite direction 
{inverse current.) 

But during the time that the circuit is closed, whatever 
may be the direction in which the current is passing, the 
animal no longer presents any of these phenomena. We 
shall soon see what kind of action ought to be attributed 
to the latter during the time of its passage along the nerves. 
If the current be applied to the nerves in such a way that 
it passes across the nerve instead of along it, the contrac- 
tions are more feeble ; and even^ entirely cease when the 
experiment is conducted in such a? manner that all the cur- 
rent passes normally in the nerve. 

In repeating these experiments upon different rabbits we 
hiave remarked that, in general, the signs of pain evinced by 
the animal are more violent at the commencement of the 
passage of the inverse current, and that the contractions are 
stronger and more obvious at the commencement of the 
direct current. 

Whatever be the direction of th€ current in the nerves, 
it gives rise, both at its commencement and at its inter- 
ruption, to analogous phenomena ; but we constantly ob- 



228 ELECTRIC CURRENT. LeCT. XII. XIII. 

serve, that the most violent contractions are those which 
are excited during the first moments of the passage of the 
direct current. Marianini observed, that if a man close the 
circuit of a pile composed of a certain number of elements, 
by touching one pole with one hand, and the opposite pole 
with the other hand, the strongest shock is always felt in 
that arm in w^hich the direct current circulates. 

If we continue to experiment upon the same animal, all 
these phenomena more or less rapidly cease, according to 
the greater or less energy of the current, and the animal 
gives no further evidence of the passage of it. If the ani- 
mal be then left undisturbed for some time, or, if we aug- 
ment the force of the battery, the previous phenomena re- 
appear. 

But it is important to follow carefully the phenomena 
which takes place in proportion as the action of the current 
upon the animal is prolonged, and before they completely 
cease. You will observe that, w^hen the direct current is 
interrupted, the contractions of the inferior muscles (those 
which are placed below that part of the nerve to which 
it is applied) become more feeble, whereas they continue in 
the muscles of the back, and the agitation, and often the 
cries, of the animal continue. We see, also, that for the 
first few moments of the passage of the current, its effects 
are limited to contractions of the inferior muscles. When 
the current is reversed, the contractions of the muscles of 
the back, the movements of the ears, and the cries, are not 
manifested except at the moment of closing the circuit; 
while the contractions of the inferior muscles are scarcely 
perceptible. But the opposite effect takes place when we 
interrupt the circuit ; that is to say, the contractions of these 
latter muscles continue, whilst those of the back, and the 
movements of the ears disappear, and the animal ceases to 
utter cries. 



LeCT. XII. XIII. REFLEX MOVEMENTS. 229 

Two Periods in the Action of the Current on the 
JVerye5.— We must, therefore, divide into two different pe- 
riods the action of the electric current on the nerves of a 
living animal. In the first, the irritation of the nerve is 
transmitted in all directions towards its central part, as well 
as to its periphery, both at the commencement and cessa- 
tion of its action, and independently of the direction of the 
current. In the second period, the excitation of the nerve 
is transmitted towards its periphery, during the first mo- 
ments of the action of the direct current, and at the instant 
of the interruption of the inverse current : on the contrary, 
when the direct current is interrupted, or when the circuit 
of the inverse one is being closed, the irritation of the nerve 
is transmitted towards the brain. 

I may express the whole of these results in more simple 
terms : the current acts in the direction in which it is trans- 
mitted, when it begins to circulate in the nerve, and in the 
opposite direction w^hen it ceases to circulate. 

Before we proceed further, we must inquire how the 
electric current can occasion contractions of the muscles of 
the back and of the head, by acting, as we have seen in 
the preceding experiments, on nerves which are not dis- 
tributed to them. 

If you divide the spinal marrow of a rabbit transversely, 
and cause an electric current to pass along the crural nerve, 
you will observe that the contractions are, in this case, con- 
fined to the muscles situated below the point where the 
spinal marrow was divided ; and if this was effected near 
its inferior extremity, no contractions will occur in the 
muscles situated above the excited nerve. 

Refiex Movements. — The contractions excited in the 
muscles situated above the irritated nerve by an electric 
current, are then reflex movements. The excitation of this 
nerve is transmitted to the spinal marrow, and the latter, 



230 ELECTRIC CURRENT. LeCT. XII. XIII. 

by a reflected action, produces contractions of muscles not 
supplied by the nerve irritated by the current. We may, 
therefore, say, in the language of Dr. Marshal Hall and 
other modern physiologists, that the electric excitation of a 
nerve which was at first centripetal, is transformed into a 
centrifugal one. 

Effects on dead Animals. — Hitherto I have demonstrated 
the laws of the action of the electric current on the nerves 
of a living animal. I must now speak of this action on the 
nerves of animals which have been recently killed. 

By submitting recently killed rabbits, prepared as in the 
preceding experiments, to the influence of a single element, 
we obtain the contraction of the inferior muscles, at the 
moment when the circuit of the direct current is closed, and 
when that of the inverse current is interrupted. By acting 
with a more powerful battery, the contractions of the same 
muscles take place as well as when the current begins to 
circulate as when it ceases, whichever its direction may be. 
After it has continued to pass for a certain time, contractions 
no longer ensue, except at the commencement of the direct, 
or at the cessation of the inverse current. 

These phenomena may be verified an all animals, but 
they are most easily shown in the frog. 

I have here one of these animals, prepared according to 
Galvani's usual method, and from which the bones of the 
pelvis, and the lumbar vertebrae have been removed. This 
frog is placed astride with one foot in one glass full of 
water, and the other foot in another glass of water. 

When I plunge the two conductors of a pile into these 
glasses, you will at first observe that the frog will leap out ; 
and if we retain it forcibly in its place, contractions take 
place in both legs both w^hen opening and closing the cir- 
cuit, and, consequently, in the limb in which the current is 
direct, as well as in that in which it is inverse. But if we 



LeCT. XIT. XIII. EFFECTS ON DEAD ANIMALS. 231 

continue the experiment, we soon perceive the alteration 
already described ; that is to say, at the moment when the 

Fig. 17. 




Experiment to illustrate the Action of a direct and an inverse Current on the Nerves 

of a Frog. 

circuit is completed, one limb only contracts, namely,- that 
in which the current is direct ; while, on the contrary, when 
we interrupt the circuit, the contraction takes place in the 
other limb, namely, in the one traversed by the inverse cur- 
rent. This series of phenomena is manifested, more or less 
speedily, according to the strength of the current, and the 
vivacity of the animal, but it is never absent. Thus, then, 
the frog is not only a galvanoscope of extreme sensibility, 
but it is also an instrument which may perform the office of 
a galvanometer, and like this, indicate the direction of the 
current which circulates in a portion of its nerves. 

It was Marianini who first observed that contractions were 
obtained at the interruption of the circuit, and not at the 
moment when it was closed. To succeed with this expe- 
riment, it is necessary to introduce a frog into the circuit 
of a pile, and to close this by touching one pole with one 
hand, and plunging the fingers of the other into the liquid 
in which one of the extremities of the frog are also im- 
mersed. At first the current which circulates is very feeble, 
in consequence of the bad conducting power of the hand, 
but it goes on increasing in proportion as the fingers imbibe 



232 ELECTRIC CURRENT. LeCT. XII. XIII. 

more of the liquid ; and the frog does not suffer any effect 
at the commencement of the current, but only at its inter- 
ruption. 

Effects on the Muscles. — We have hitherto caused the 
current to act on the nerves of animals, and have deter- 
mined the laws of this action. We have also examined 
the case in which it circulates in the entire animal, by tra- 
versing at the same time nerves and muscles. It remains 
now for me to notice the action of the current on the mus- 
cular fibre alone. 

The difficulty surrounding such an investigation may be 
easily conceived ; for we cannot with certainty remove 
every trace of the nervous substance, even when we remove 
from a muscle all its nervous filaments visible to the naked 
eye, as well as those which are only perceptible by the aid 
of a magnifying glass. However, it is upon a muscle thus 
deprived, as carefully as possible of its nervous filaments, 
that we are obliged to operate, and the following are the 
results obtained : — 

By passing the current from twenty to thirty elements 
through the pectoral muscle of a pigeon, from which the 
nerves have been removed, as just mentioned, we always 
observe, that contraction takes place when we close the 
circuit. This contraction, moreover, lasts but for an instant, 
and appears to consist in a momentary shortening of the 
fibres. Whatever may be the direction of the current in 
relation to that of the muscular fibres, the phenomenon is 
the same. If the circuit be kept closed, and the passage 
of the current through the muscle be continued, the contrac- 
tions reappear on opening the circuit. They are weaker 
than when we close the circuit; nnd if the passage has been 
prolonged for some time, they are entirely absent at the 
interruption of the circuit. 

In general, the contractions obtained by acting on the 



LeCT. XII. XIII. EFFECTS ON THE MUSCLES. 233 

muscle at the closure of the circuit, are more persistent 
than those which take place at the opening of it. The 
latter re-appear when the intensity of the current is aug- 
mented. 

We may, therefore, conclude, that when the electric 
current acts on a muscular mass deprived of its visible 
nervous filaments, it excites contractions therein, both when 
the circuit is closed and when it is interrupted, whatever 
may be the direction of the current relatively to that of the 
muscular fibres ; and, also, that the contractions which take 
place when the circuit is opened are the first to disappear. 

If the discharge be that of a Leyden bottle, which is made 
to pass across a muscle, — for example, the gastrocnemius 
of a frog, — it is curious to observe that the muscle contracts 
and continues in this state. 

It now remains for me to notice the various circumstances 
which modify the action of the current on the nerves and 
muscles of living, or recently killed animals. 

The voltaic alternatives ^ of which I am now about to speak, 
are the result of the same passage of the current in the 
nerve. Observe in what this phenomena consists. We 
put a frog, prepared in the usual way, across two small 
glasses, containing pure, or slightly saline water, in such a 
way that the spinal marrow is immersed in one glass, and 
the legs in the other. We then close the circuit. If we 
allow the current to circulate for a certain time, say twenty 
or thirty minutes, according to the strength of the current, 
and then open it and close it again, no further contractions 
are obtained. But by reversing the direction of the current, 
the contractions re-appear; and they cease again, more 
speedily than in the preceding one, when the passage of 
the current has been prolonged. By again reversing the 
direction of the current, that is, by re-establishing it as it 
was at the commencement of the experiment, the contrac- 



234 ELECTRIC CURRENT. LeCT. XII. XIII. 

tions re-appear. These alternations maybe repeated a cer- 
tain number of times on the same animal. The intervals 
of time between the passage of the two currents, depend 
on the intensity of the current and the vivacity of the 
animal. 

It is easy to prove that the diminution of the excitability 
of the nerve from the passage of the current, is principal- 
ly manifested in the portion traversed by the latter. Sup- 
pose we have passed a current through the nerve of a frog, 
prepared after Galvani's method, and have prolonged the 
action until the contractions have ceased ; if w^e then apply 
the conductors to a portion of the nerve more distant 
from the brain than that on which we first acted, we soon 
observe the contractions re-appear according to the laws 
already laid down. By continuing these experiments, 
exposing successive portions of the nerve more distant from 
the brain, similar results are obtained. We may therefore 
say, that the excitability of the nerve, roused by the current, 
retires towards the periphery according as its vitality be- 
comes extinct. When we act on a living animal in the way 
described, we find that the signs of pain evinced when an 
electric current traverses its nerves, are also manifested 
when W'C act on those parts of the latter, nearer and nearer 
to the brain, according as its vivacity diminishes by the 
prolonged passage of the current. In both cases, it is the 
excitability of the nerve which becomes weakened by the 
passage of the current ; and, as when a muscular mass is 
traversed by the latter, it is certain that the whole, or at 
least the greater part of the current passes, not by nervous 
filaments, but by the muscles, which are better conductors, 
it is natural that these filaments should preserve their excita- 
bility, and that they should be found also excitable by the 
current. 

Effects of the Current on poisoned Animals. — It was im" 



LeCT. XII. XIII. EFFECTS ON POISONED ANIMALS. 235 

portant that the action of the current upon poisoned animals 
should be examined. For this purpose I made a considera- 
ble number of experiments, the principal results of which 
I shall now state. 

The different methods of proceeding to ascertain the 
effects of various toxicological agents upon the excitability 
of the nerves to the passage of the electrical current may 
be reduced to two: one consists in ascertaining the number 
of elements necessary to excite contractions both in poison- 
ed and in uninjured frogs ; the other and preferable method, 
is to compare the time required for the passage of a given 
current to destroy entirely the nervous excitability of a 
poisoned animal, and of another animal killed in the usual 
way. 

Animals which have perished in hydrogen, azote, car- 
bonic acid, and chlorine, and are submitted to the passage 
of the electric current through their nerves, present no 
difference from other dead animals w^hich have not been 
subjected to the action of these gases. But this is not the 
case with those killed by hydrocyanic acid, or by the re- 
peated discharges of a large battery through the spinal 
marrow. In these cases the current furnished by one, or 
even many elements, applied upon the nerves of an animal 
excites no contraction there, or if there be any they are very 
slight, and the passage of the current for a few seconds is 
sufficient to destroy them entirely. The muscles, however, 
when submitted to this same current, give very evident signs 
of contraction ; thus proving what I have before mentioned, 
that the muscular fibre must possess the property of contract- 
ing, under the influence of the current, independently of 
the nerve. 

Lastly, if the animals on which we act by the electric 
current have died in sulphuretted hydrogen, we never 
obtain contractions unless very powerful currents are em- 



236 ELECTRIC CURRENT. LeCT. XII. XIII. 

ployed, and even then the contractions soon cease ; and 
that, whether we act on the nerves or on the muscles. 

Effect of tying the Nerve. — I wish also to show you some 
differences observed in the physiological action of the cur- 
rent when the nerve on which we act has been tied. I 
expose and isolate the crural nerve of a rabbit, put a liga- 
ture on the nerve at about its middle, and afterwards 
transmit the current through the part above the ligature, 
namely, towards the brain. I obtain contractions of the 
back and signs of pain, both when I open the circuit and 
when I close it, whatever may be the direction of the current. 
Very soon, these effects are produced only at the com- 
mencement of the passage of the inverse current, and at 
the cessation of the direct one. If, on the contrary, I 
transmit the current below the ligature, I first obtain con- 
tractions of the leg, w^hether I open or close the direct or 
inverse current, and very soon, as usual, contractions cease, 
except at the first moment of the direct current, and at the 
termination of the inverse one. From these facts, then, it 
appears that a ligature on a nerve produces no other in- 
fluence than that of insulating the effects of the current ; 
that is, of producing the effects of its action on the nervous 
centres, separately from those which it has when acting 
upon the extremities of nerves. It is unnecessary to add, 
that if we operate on a dead animal, we obtain no signs 
indicative of pain. 

In order to avoid errors in repeating these experiments, 
care must be taken to insulate the nerve completely from 
the moist parts which surround it, and to apply the ligature 
tightly. The best way of proceeding is to use a frog pre- 
pared in the usual manner, and then to suspend it by its 
nerve with a silk thread. In this way we are sure that no 
moist part around the nerve can divert any portion of the 
current ; but if we neglect these precautions, a certain por- 



LeCT. XII. XIII. DIRECT AND INVERSE CURRENT. 237 

tion of the current may pass above or below the ligature, 
and thus confuse the results. 

When we apply the two poles, one above, and the other 
below the ligature, as the current is not interrupted, but 
only weakened, it follows that the phenomena w^ill be the 
same as if there w^as no ligature, except that they will be 
more feeble. 

Different Effects of the Direct and Inverse Current. — I 
have hitherto purposely refrained from noticing here, the 
difference which exists in the loss of excitability produced 
by the passage of the electric current in the nerve, according 
to its direction. When we transmit the current in a frog 
prepared in the manner I have described, and placed 
across two small glasses, we at first obtain contractions in 
the limbs both at the commencement and at the termina- 
tion of the passage of the current, whatever be its direction. 
The second period of excitability, already described, soon 
follows, and in this there is contraction in the limb traversed 
by the inverse current, only at its cessation, and in that 
traversed by the direct current only at its commencement. 

Let us now examine some phenomena which present 
themselves, when we continue the passage of the current. 
All contraction disappears, after a certain time, in the limb 
traversed by the direct current, and we see contractions 
continue in that limb only which is submitted to the action 
of the inverse current, when the latter is interrupted. This 
result, which may be obtained either on a living or a dead 
frog, which maybe also produced by causing the current to 
act on the serves only, evidently proves that the excitability 
of a nerve is much more weakened by the passage of the 
direct current, than by that of the inverse one. I shall 
here show you some facts relating to this subject, which 
appear to me clearly to prove that not only the inverse cur- 
rent affects less the excitability of the nerve than the direct 



238 



ELECTRIC CURRENT. 



Lect. XII. XIII. 



one, but that it acts in a directly opposite way ; namely, that 
whilst the direct current diminishes the excitability, the 
inverse current augments it. 



Fig. 18. 




Three views of Breguet's Apparatus fur measuring the Contraction of Mtiscles 
produced by the Electric Current. 

If the nerve be traversed for several hours, say three or 
four, by the inverse current, it frequently happens that at 
the interruption of the circuit, the limb suffers a very vio- 
lent contraction which lasts for a certain number of se- 
conds,, and might, therefore, be termed tetanic. This 
phenomenon ceases when we again close the circuit; but 
it is important to observe, that at the moment when we 
thus close it, there is a &esh contraction, after which the 



Lect. XII. XIII. breguet's apparatus. 239 

limb returns to its natural condition. This contraction, 
which occurs when we close the circuit of the inverse cur- 
rent, does not exist longer than the first moments of the 
experiment, and it has re-appeared after the very prolonged 
action of the same current. 

It was desirable to ascertain whether the contractions ob- 
tained on opening the circuit of the inverse current, in- 
creased within certain limits, in proportion to the time the 
current remained closed. To ascertain this it was neces- 
sary to measure the contraction, and this I did by means of 
an apparatus contrived by Breguet. 

This apparatus consists of a solid brass support, a b, 
fixed upon a wooden stand in which slide two pieces of 
metal, c d, capable of being fixed in different places by 
means of screws of pressure {vis de pression.) The piece of 
metal, c, is furnished with a vice, e, in which is to be held 
the morsel of spinal marrow of the prepared frog, and is 
fastened there by three screw^s. The other piece, f, of a 
fork-shape, is provided with a hole in each extremity of the 
fork, in which a very fine wire, g, is fixed or regulated. 
At one end of the wire is a fork, to which is aflBxed the 
claw of a frog; the other end of the wire is attached to a 
silken thread, which winds round the little pulley, i. Upon 
this another thread of silk is wound in contrary sense to the 
former, and to this attached a small leaden weight, o. The 
axis of the pulley is furnished with a kind of double index, 
p Q, in the form of a semicircle. The axis is fixed upon 
two pivots, which admit of being more or less approxi- 
mated. One of these pivots is the centre of a circle, r s, 
which bears a division. A long ivory needle, t v, is at- 
tached to this pivot ; it is very light, and turns with the 
slightest possible touch. The use of this ivory index is ob- 
vious. In effect when this index is brought in contact with 
the semicircular one,,? q, which is attached tothe axis of 



240 ELECTRIC CURRENT. LeCT. XII. XIII. 

the pulley, and the pulley is put in motion, the movement is 
comraunicated to the ivory ■index, and this latter will stop 
at the point at which it arrives in its gyration, even when 
the pulley is brought back to its former position by the httle 
weight. It must be allowed, that without such an index 
as the one described, it would have been impossible to have 
judged of the extent of the movement of the pulley produced 
by the contraction, on account of its short duration. The 
weight I have been in the habit uf using is 0*600 gramme 
[= 9*266 grs. troy,] sufficient to allow of the limb return- 
ing to its position after the contractions have ceased ; a 
heavier weight than this w^ould stretch the nerve too much. 

The following is a description of the manner in which I 
pass the current. In every case it is always a half frog, 
deprived of the muscles and bones of the pelvis, which is 
used for this experiment. The half frog is thus reduced to 
a portion of spinal marrow, which is held in the vice, the 
nervous filament, the thigh and the leg, minus the claw, 
which is cut off'. The little hook of the wire, g, is inserted 
between the bone and the tendo-achillis. Lastly, a gilded 
steel needle is thrust into the muscles of the thigh, as near 
as possible to the insertion of the nerve ; and to this needle 
is soldered a very fine copper wire, k, covered over with 
silk, which is fixed to the piece of ivory, e. It is quite 
clear that in order to pass the current through the nerve, 
nothing more is wanting than to touch the support, a b? 
with one pole of the pile, in any point whatever, and the 
wire which is soldered to the steel needle with the other 
pole. In all my experiments I made use of a Wheatstone 
pile, the elements of which, as every one knows, are formed 
of an amalgam of zinc, contained in a cylinder of wood 
immersed in a solution of sulphate of copper, in which the 
copper of the pile dips. 

I cannot here give you all the details of the numerous ex- 



Lect. XII. XIII. breguet's apparatus. 241 

periments I have made with this instrument, for the purpose 
of determining the force of the contraction excited by the 
electric current in different cases. But here are the general 
conclusions at which I have arrived : — 

1st. The contraction excited by the electric current, trans- 
mitted along a nerve in the direction of its ramification, and 
which we call direct^ is always more energetic than that 
which this same current produces when passing along the 
nerve in the opposite direction. 

2dly. The direct current weakens and rapidly destroys 
the excitability of a nerve ; whilst the passage of the inverse 
current augments it within certain limits. 

3dly. To produce these effects, the action on the nerve, 
of the direct as well as of the inverse current, ought to be 
continued for a certain time, which will be longer in pro- 
portion as the excitability of the nerve is weaker. 

It is very easy to prove, by experiment, the most impor- 
tant of these conclusions; that is to say, that when the direct 
current traverses the lumbar nerve of a frog for twenty or 
thirty minutes, there are no further contractions, either when 
interrupting or closing the circuit ; on the contrary, the con- 
traction obtained by opening the circuit of the inverse cur- 
rent, after many hours' passage, scarcely differs from that 
which occurred at first, when the nerve was endowed with 
great excitability This difference in the excitability of a 
nerve, according as it has been submitted to the passage of 
a direct or inverse current, can be observed whatever may 
have been the manner in which the nerve is stimulated. 
When we operate with the inverse current on a very ex- 
citable nerve, and one which has never before been sub- 
mitted to the passage of the current, it is impossible to dis- 
cover any difference between the contraction excited by the 
opening of the circuit of this current after the passage has con- 
tinued for one second, and that which occurs after the passage 
16 



242 ELECTRIC CURRENT. LecT. XII. XIII. 

has been continued for ten or twenty seconds. It does, how- 
ever, exist: but to appreciate it, it is necessary to proceed 
more rapidly. If the passage of the inverse current be limited 
to a small fraction of a second, we find on opening the circuit, 
a weaker contraction than that which is obtained after the 
current has circulated for one or more seconds. It is very 
easy to prove this, by closing the circuit by the aid of a 
wheel furnished with a metallic tooth, and to which we at- 
tach one of the wires of the pile during its rotation. When 
the nerve has lost part of its excitability, we then readily 
perceive that the contraction manifested on opening the cir. 
cuit, increases proportionably to the time that the circuit has 
been closed. The greatest effect of the passage is obtained 
at the end of fifteen or twenty seconds. It is needless to 
say, that these effects do not continue to increase on a dead 
animal. 

Influence of Repose. —F'lnaWy^ it remains for me to notice 
the influence produced by repose on a nerve which has been 
submitted to the action of the current. If the nerve has 
been traversed by the direct current, repose restores a por- 
tion of its excitability ; if it has been traversed by the in- 
verse current, it loses by repose a part of that excitability 
which it had acquired under the influence of the current. 
When the nerve is very irritable, a very short repose suf- 
fices to restore the excitability lost by the action of the 
direct current ; it is the same with the augmentation occa- 
sioned by the inverse current ; almost as soon as it is inter- 
rupted, the nerve returns to its normal condition. In pro- 
portion as the excitability diminishes, the duration of repose 
necessary for giving or arousing the excitability acquired 
under the passage of the current, augments. 

I must here add, that the relation between the muscular 
contractions and the current is established in a more inti- 
mate manner,, by measuring this contraction and comparing 



LeCT. XII. XIII. ACTION OF CURRENT ON NERVES. 243 

it with the quantity of electricity which excites it. I have 
lately proved, by employing Breguet's apparatus before 
mentioned, that this contraction is proportionate to the 
quantity of electricity which excites it. 

Theory of the Action of the Current on theJVerves. — With 
the knowledge of these facts, all of which I have recently 
established by a great number of experiments, I hope to be 
enabled to give a very simple theory of the action of the 
electric current on the nerves, and of the phenomena which 
it produces in animals. 

No experiment demonstrates that the electric current ex- 
cites muscular contraction during its passage in the nerves. 
This passage only modifies the excitability of the nerve. 
Contraction is constantly produced by the effect of the 
electric discharge, properly so called, namely, by the neu- 
tralization of the two opposite electrical conditions accu- 
mulated at the poles, and which give the spark. Every 
one knows, that when we close the circuit of a pile, as well 
as when we open it, there is a spark. Under precisely the 
same circumstances the current always excites contractions 
of a frog excited by touching its nerve with the armatures 
of a Leyden bottle, which has already been discharged; 
several times by a metallic arc, to be convinced how ex- 
cessively feeble is the discharge capable of producing this 
effect. A bottle which, as we have stated, has been already 
discharged many times, can yet produce fifteen or twenty 
contractions in a frog. 

On the discharge of the bottle, we likewise see that the 
contraction of the limb, traversed by the inverse discharge, 
first ceases, whilst that which is provoked by the direct 
discharge continues. 

There is no difficulty, therefore, in understanding w^hy, 
when the excitability of the nerve is lessened, the spark 
produced by the interruption of the direct current should 



244 ELECTRIC CURRENT. LeCT. XII. XIII, 

excite no farther contractions. With the inverse current 
we obtain the contraction by the spark at the opening of 
the circuit, because, in the interval of its passage, the ex- 
citability of the nerve has increased. This augmentation 
disappears immediately the current ceases to act, and this 
is the reason why the spark no longer excites contractions 
when we subsequently again close the inverse circuit. 

With these notions we can understand the fact of the 
voltaic alternatives: when a nerve has been for some time 
traversed by the direct current, and has lost its excitability, 
it no longer suffers contraction, notwithstanding that there 
may be a spark at the closure, and at the interruption of 
the current. The inverse current restores to the nerve a 
portion of its excitability, and its contraction re-appears 
when we open the circuit. If from the action of the inverse 
current we return to that of the direct current, the contrac- 
tions which are obtained during the short time that the nerve 
preserves the excitability acquired by the passage of the 
inverse current, will be more energetic, inasmuch as we 
have seen that the direct discharge produces on a nerve, 
endowed with a certain degree of excitability, a stronger 
contraction than the inverse one* 

Effects on other Parts of the JYervous System. — To com- 
plete this lecture, it only remains for me to speak of the 
effects which the electric current produces when applied to 
different parts of the brain, to the nerves of sensation, to the 
roots of the spinal nerves, and to the ganglionic nerves. I 
regret that a subject so important has not hitherto been 
properly investigated. We may say that every thing yet 
remains to be done: the few words which I can say to you 
on the subject will prove it. 

Effects on the Brain. — I applied the conductors of a pile, 
formed of several elements, to the cerebral hemispheres, 
and to the cerebellum of the brains of a living animal; and 



LeCT. XII. XIII. EFFECTS ON SPINAL MARROW. 245 

I introduced the conductors into the very substance of these 
organs, without perceiving either convulsions or signs of 
pain. But by bringing the conductors in contact with the 
tuhercula quadrigemini, the crura cerebri^ and medulla oblon- 
gata^ we obtain very violent convulsions throughout the 
body, and the animal gives signs of suffering. 

Effects on the Spinal Marrow and the Roots of its JVerves. — 
In conjunction with Longet, I examined the action of the 
electric current upon the roots of the spinal nerves, and on 
the fasciculi of the spinal marrow. The following are the 
results obtained. With the anterior roots, which are for 
motion, there was, as usual, in the first period, contractions 
produced both when we closed and when we interrupted 
the circuit, whatever was the direction of the current. In 
the second period of excitability, we obtained, by acting 
upon the anterior roots, the opposite effect to that which 
took place upon the mixed nerves; the inverse current 
excited contractions in the first moments of its passage, and 
none when it ceased ; the direct current, on the contrary, 
produced them when it was interrupted, and not when we 
closed it. It is unnecessary to add, that contractions were 
never produced when we acted upon the posterior roots, 
provided that we had divided the anterior ones. The an- 
terior fasciculi of the spinal marrow offered the same phe- 
nomena as the corresponding roots. These differences ap- 
pear to me of the very highest importance. 

I have recently found that a mixed nerve, after having 
been -submitted to a great number of successive discharges, 
such as can be obtained with an electro-magnetic machine, 
presents, ybr a certain time, the phenomena of the anterior 
roots now described. 

This study, I repeat, will be of the highest importance 
for the physics of the nervous system ; and the facts related 
lead us to assume that the differences obtained with different 



246 ELECTRIC CURRENT. LeCT. XII. XIII. 

nerves are due rather to a difference of structure than to a 
different state of the nervous fluid. 

Effects on the JYerves of Sensation. — Let us now pass to 
the nerves of sensation. Magendie caused the current to 
pass through the optic nerve of a living animal without 
obtaining contractions or symptoms of pain. In operating 
on himself, by touching with the extremities of a pile^ 
formed by a single element, the ear and the eye, or the ear 
and the tongue, or the eye and the tongue, he obtained 
sensations of sound, flashes of light and a peculiar taste. 
These effects could only depend on an action exercised by 
the current on the sensorial nerves of these organs, and not 
on the contractions excited in the muscles dependent on 
them. In fact, a very feeble current, insufficient to excite 
the slightest muscular movement, is capable of acting upon 
the senses. The peculiar taste cannot be attributed to the 
impression exercised upon the tongue by substances pro- 
duced by the decomposition of the salts of the saliva effected 
by the pile; for a very feeble current, and one that is unable 
to cause this decomposition, is yet sufficiently strong to give 
rise to the electric sensation upon the tongue. 

Effects on the Ganglionic JVerves.—K few words, in the 
last place, on the action of the current on the nerves of the 
ganglionic system. For the little that we know on this 
subject we are indebted to the celebrated Humboldt. 

When we transmit a current through the heart of a 
recently killed animal, a few instances after pulsations have 
ceased, we observe that this organ recovers its usual move- 
ments some time after the passage of the electric current ; 
and that these movements are preserved for a certain time 
after the organ has been withdrawn from the action of the 
current. 

If, instead of waiting until the natural movements of the 
heart have entirely ceased, we transmit the current when 



LeCT. XII. XIII. GANGLIONIC NERVES. 247 

they are becoming weaker, we then perceive that when 
the latter has acted upon the heart for some time, the 
movements become more frequent, and the augmented 
frequency continues for several seconds after the current 
has been interrupted. 

The same effects take place with the vermicular move- 
ment of the intestines when these organs are subjected to 
the influence of the current. 

If we reflect on the importance which the ganglionic 
system possesses in the performance of the organic Junc- 
tions of animals, we can easily understand how very insuf- 
ficient are the researches hitherto made on this subject. 

The difference of action exercised by the current upon 
the nerves of the life of relation, and on those of organic life, 
is very marked. In the former, its effects are manifested 
only in the first and the last moments of its application ; 
in the latter, on the contrary, they are slow to appear, 
continue during the passage of the current, and even per- 
sist after it has been interrupted. 

Effects of the Interrupted Current, — Having now exa- 
mined the influence exercised upon the irritability of nerves 
by the passage of the continued current, it remains for us 
to examine the effects produced by the current interrupted 
and re-established at short intervals, in such a way that its 
action is very frequently repeated upon the nerve. 

For this purpose I fix to the table, by means of small nails, 
a frog prepared in the usual manner. I connect one of 
the conductors of the pile with one of the nails, and with the 
other conductor I touch, many times successively, another 
nail, thus establishing and interrupting successively, the 
circuit, in a very short time. We see the frog violently 
extending its limbs, as if affected with tetanic convulsions, 
whether the current which thus traverses it by jerks be 
either direct or inverse. 



248 ELECTRIC CURRENT. LeCT. XII. XIII. 

The excitability of the nerves of a frog, thus tetanized 
by the passage of the electric current, is very feeble when 
compared with that of another frog upon which a continued 
current has been made to act. I have often repeated this 
comparative experiment by submitting two frogs, prepared 
alike, the one to the action of the continued current pro- 
duced by forty-five elements, and the other to that of a 
pile of the same force, but in which the current was inter- 
rupted and re-established at short intervals. 

In each of these cases the experiment lasts ten or fif- 
teen minutes. By submitting afterwards, the lumbar nerves 
of these frogs to the passage of the direct current, I ob- 
served that a greater number of elements was required to 
cause contraction in the animal which had been previously 
submitted to the interrupted current, than in that which 
had been subjected to the direct one. I also satisfied my- 
self of the difference of the excitability of these two frogs, 
by causing a continued current to act upon them at the 
same time ; the diminution was constantly greater in the 
one which had been submitted to the influence of the inter- 
rupted current. 

Marianini, also, found, that by comparing two frogs, one 
of which had been traversed by a continued current al- 
ways in the same direction, and the other by a current 
transmitted sometimes in one and sometimes in the other 
direction, that the excitability of the nerves, was less ex- 
hausted in the first animal, than in the second one. 

This great diminution of excitability in the nerves, or to 
speak more precisely, in the nervous force, induced by the 
passage of the current renewed at very short intervals, has 
been clearly demonstrated by the experiments of Masson. 
The apparatus by which this philosopher succeeded in trans- 
mitting the electric current a great number of times through 
an animal, and interrupting it for very short intervals, con- 



Lect. XII. XII. masson's apparatus. 



249 



sisted of a metallic wheel, r, supported on a metallic axis, 
and turned, by means of a handle, upon two amalgamated 
cushions. One of these was in communication with one of 
the poles of a pile,p, whilst the second pole was in contact with 
a wire, which, after being wound spirally around a cylinder 
of soft iron, m, terminated in a fixed metallic plate applied 
to the teeth of the wheel. 

When we revolve the wheel, the circuit closes every 
time the plate touches one of the teeth, and the circuit is 

Fig. 19. 




Masson's Apparatus. 



interrupted when one of the non-metallic spaces comes in 
contact with it. By applying the moistened hands to the 
two extremities, a and b, of the conductor when the wheel 
revolves, a series of violent shocks is obtained. If the 
movements of the wheel be sufficiently rapid, these succes- 
sive passages produce a very painful tension in the arms ; 
the experimenter cannot let go the conductors, but invo- 
luntarily grasps them with great force. 

Masson, by means of this apparatus, and a pile, formed 
of a small number of elements, succeeded in killing a cat 
in five or six minutes. 

He found that these shocks, and this spasmodic tension, 
disappeared by communicating a great rapidity of the wheel. 
Pouillet proved, that when the duration of the interval be- 



250 ELCTRIC CURRENT. LecT. XII. XIII' 

tween the two passages of the current is about ^^o of a 
second, the interruptions were no longer perceptible, and 
the effect produced was the same as with a continued cur- 
rent. 

I have here a rabbit, which I shall submit to the pas- 
sage of a current by means of Masson's wheel. One of 
the conductors of the pile has been introduced into its 
mouth, the other communicates with the muscles of the 
back. Although the pile consists only of ten elements, the 
animal dies withia a few seconds. These powerful effects 
must certainly be ascribed to the great loss of nervous 
power effected in a very brief space of time. 

These results appear to me to explain readily Weber's 
observation, that the pulsation of the heart ceases when the 
interrupted current is made to act on its nerves. 

Therapeutical Use of the Current. — I cannot conclude this 
lecture without stating some of the therapeutical applica- 
tions made of the electric current, and founded upon the 
scientific principles, which I have made known to you. 

In Paralysis. — Abstraction being made of all purely 
theoretical ideas, and independently of all hypothesis of 
the nervous force, we may admit that, in certain cases of 
paralysis, the nerves undergo an alteration analogous to 
that which they would suffer if they had been subjected to 
a continued passage of the electric current. We have seen 
that, in order to restore to a nerve the excitability lost by 
the passage of this current, it is necessary to subject it to 
the action of the inverse current. 

I must add, in favour of the efficacy of the therapeutic 
use of this current, that a limb, although paralyzed, con- 
stantly suffers some contractions when it is submitted, either 
to the passage of a current or to the action of electric dis- 
charges ; and these contractions favour the restoration of 
the functions of the muscles. Experiment confirms these 



Lect. XII. XIII. masson's apparatus. 251 

ideas : divide the two sciatic nerves of a living frog, allow 
one of the two limbs to remain quiet for ten, fifteen, or 
twenty days, and submit the other, two or three times a-day, 
to the action of the current. The latter will continue to 
contract, whilst the other will fail to give any contractions 
when the current is applied to it. 

I am anxious to state to you some rules w^hich I con- 
sider as important in the application of the current to the 
treatment of paralysis. You should always commence by 
employing a very weak current. This precaution seems to 
me now more important than I formerly believed it to be, 
having seen one paralytic patient seized with true tetanic 
convulsions under the action of a current furnished by a 
single element. Take care never to continue the current 
for too long a period, especially if it be energetic. Apply 
the interrupted current in preference to the continued one ; 
but after twenty or thirty shocks, at the most, allow the pa- 
tient to have a few moments' repose. Both practice and 
theory seem to prove, that the interrupted current is more 
useful than the continued one. 

A pile, with Masson's wheel, or still better, the electro- 
magnetic machine, is the most convenient apparatus for 
this purpose. Electro-magnetic apparatus are now con- 
structed, in which the interruptions of the current are made 
without the necessity of an assistant. 

We may employ, as conductors, two ribands of sheet 
lead or copper. The extremities, which are placed in con- 
tact with the skin, should be covered with cloth moistened 
with salt and water. In some cases, it is useful to employ, 
as extremities of the conductors, acupuncture needles. 

The number of authentic cases of paralysis cured by the 
electrical treatment, is already sufficiently great to encourage 
physicians and patients to persevere in its use. Perse- 
verance indeed is indispensable in the application of the 



252 ELECTRIC CURRENT. LeCT. XII. XIII. 

electric current, for without it, successful results are impos- 
sible. 

In Tetanus. — The use of the electric current has been 
suggested in another malady, namely, tetanus. I believe 
I am the first who has attempted its application to man. 

The principles on which is founded its employment for 
the cure of this disease are the following. A current which 
circulates by jerks in an animal during a certain time, pro- 
duces tetanic convulsions ; the direct current, if continued 
sufficiently long, produces, on the contrary, paralysis. From 
this it was concluded, that the continued passage of the 
latter, in a tetanized limb, would destroy this condition, by 
producing a state more or less allied to paralysis. The 
truth of this conclusion is demonstrated by facts. In ope- 
rating upon frogs which have been tetanized by narcotics 
or hydrocyanic acid, we observe a fit of tetanus cease un- 
der the influence of the prolonged passage of a direct cur- 
rent. The frogs die without presenting those convulsions, 
which are observed take place when these animals have 
not been submitted to the direct current. 

The effects produced by the application of the electric 
current is a case of tetanus, which I published in the Bi- 
bliotheque Universelle (May, 1838,) appeared to me in some 
degree to prove the truth of the scientific principles which 
J have explained to you. During the passage of the cur- 
rent, the patient experienced no violent convulsions ; he was 
able to open and shut his moiith ; and circulation and per- 
spiration appeared to be re-established. Unfortunately, this 
amendment did not continue long ; the disease being occa- 
sioned, and kept up by the introduction of foreign bodies 
into the muscles of the leg. Perhaps more satisfactory 
results from the electric current may be expected, in cases 
where tetanus has not been caused by a traumatic injury : 
moreover, we ought already to be thankful in being able 



LeCT. XII. XIII. ELECTRIC CURRENT. 253 

to lessen the sufferings to which this dreadful disease gives 
rise. 

In Urinary Calculi. — Finally, it has lately been proposed 
to dissolve vesical calculi, and resolve cataract by the elec- 
tric current. It is sufficient, however, to remember, that 
the substances which compose urinary calculi are insoluble 
in water, to be convinced that such an application has no 
basis to rest on. 

In Cataract. — As for cataract, I would remark, that by 
changing the position of the poles of a current, which has 
been made to pass through an albuminous liquor, we never 
find that the albumen coagulated at the negative pole is 
redissolved at the positive pole. It is possible, therefore, 
to create a cataract, but impossible to destroy it. 

In Aneurism. — Petrequin, of Lyons, has recently pro- 
posed the use of galvano-acupuncture for curing certain 
aneurisms. This application appears to be founded on the 
property which the electric current possesses, of coagula- 
ting the serum of the blood, and, consequently, of partially 
filling up the aneurismal sac. 



254 NERVOUS FORCE. Lect. XIV. XV, 



LECTURES XIV. and XV. 

NERVOUS FORCE. 

Argument. — Characters of the nervous force; the cerebrospinal system, 
and its action; the gantjlionic system, and its action. 

Effects produced by electric irritation of the nerves, compared with those 
caused by other stimulants. 

Analog-y between the nervous force and the electric current. No evidence 
of an electric current in the nerves of a living animal. The nerves do 
not present the necessary conditions for such a current. Relation o^ 
the nervous force to electricity. Induced contraction ; illustrative ex- 
periments; facts favourable to the opinion, that it is caused by an electric 
discharge from contracting muscles ; disproof of Liebig's hypothesis of 
muscular contraction ; failure to detect the development of electricity 
during contraction. New investigations of the induced contraction ; it 
is only excited by a contracting muscle. Influence of substances in- 
terposed between the contracting muscle and the nerve of ihe galvano- 
scopic frog. Hypothesis to explain induced contraction. 

Production of nervous force; mechanical power obtained by the conver- 
sion of chemical action into heat, electricity, and nervous force. 

It may, perhaps, appear strange and almost rash for me 
to notice the nervous force, or agent, in a course of lectures 
on the physical phenomena of living beings; but I hope to 
prove, by the considerations which will follow, that the 
subject is not out of place here ; and that if, in treatises on 
physics, the chapter consecrated to the general analogies 
existing between caloric, electricity, and light, is the most 
important, and in some respects the most philosophical, so 
likewise will this lecture possess analogous advantages, at 
least in its high importance. 



LeCT. XIV. XV. CEREBRO-SPINAL SYSTEM. 255 

Characters of the JYervous Force. — I shall commence by 
briefly explaining the characters of the nervous force and 
its laws, according to the present state of physiological 
science. 

Cerebrospinal System. — All animals having a certain 
degree of development, possess organs, by which they are 
enabled to influence their muscles, and by the intervention 
of which they perceive external actions. These organs 
constitute the cerebro-spinal nervous system, which is prin- 
cipally composed of an infinite number of ramifications, 
disseminated throughout the body of the animal, and uniting 
in a central mass, constituted by the brain and spinal 
marrow. 

If we divide one of these ramifications in a living animal, 
and afterwards touch, with either a red-hot iron or potash, 
or wound with a needle, or pull with pincers, the portion 
which remains in communication with the cerebro-spinal 
axis, the animal manifests evident signs of pain ; but if we 
apply these irritants below the section or ligature of the 
nerve, no signs of pain are exhibited, and we perceive, 
merely, contractions in the muscles to which the irritated 
nerve is distributed. If we excite the uninjured nerve, 
both pain and contraction simultaneously occur. Lastly^ 
if we tie the nerve in two places, and then irritate the part 
included between the two ligatures, we produce neither 
pain nor contraction. The nerve, then, has no other office 
than that of transmitting and propagating the action of the 
stimulant applied to it. This double action consists in a 
sensation carried to the brain, and in a muscular contraction 
communicated to the muscles. 

The physiologists, Bell, Magendie, Muller, Pandyza, and 
others, have discovered that there are some nerves which, 
when excited, merely produce muscular contractions, and 
others which, when submitted to the like irritation,, only 



256 NERVOUS SYSTEM. Lect. XIV. XV. 

provoke pain. The anterior and posterior spinal nerves, 
and some other nervous branches, possess a single function 
only. 

Flourens Longet, and other physiologists, have also dis-. 
tinguished in the nervous centres, some parts which preside 
over sensations only, and others, again, exclusively de- 
voted to movements. 

A nervous fasciculus is made up of a great number of 
filaments, every one of which is separately able to transmit 
the influence of the will, or of some stimulant, without the 
other filaments with which it is in contact, participating in 
the action. 

Ganglionic System. — Besides the cerebro-spinal, there 
exists a second nervous system, which, notwithstanding its 
numerous connexion with the first, does not, when irritated, 
excite either movements or sensations. It is the ganglionic 
nervous system, composed of ramifications, chiefly dis- 
tributed to the apparatus of organic life. These ramifica- 
tions gradually unite, interlace with each other, and have 
in their interstices a globular matter, which seems also to 
exist in the central masses. 

In this system, irritations, manifested by certain peculiar 
movements, excited chiefly in the intestines, are slowly 
propagated, and continue to be so, even w^hen the irritating 
action has been removed. A muscle, which has been 
deprived for a certain time of all communication with the 
centres or ganglia, of this system, loses the property of 
contracting under the influence of irritation of its cerebro- 
spinal nerves. 

These few words concerning the nervous action will, I 
hope, be sufficient to make you understand the importance 
of the results to which we are come on the physiological 
action of the electric current. 

Peculiarities of Electric Irritation of the JSTerves. — I con- 



LeCT. XIV. XV. ELECTRIC AND NERVOUS FORCES. 257 

sider it necessary to give here a summary of the principal 
differences which have been ascertained experimentally, 
between the effects produced by electric irritation of the 
nerves, and those determined by other stimulating agents, 
such as heat, chemical and mechanical actions, &c. The 
following are these different distinctions : — 

1. Electricity is the only irritant w^hich can excite, at one 
time sensation, and at another contraction, according to the 
direction in which it traverses a nerve. 

2. The electric current alone, in passing transversely 
across a nerve, produces no phenomena due to the excita- 
bility of the nerve. 

3. The electric current has no effect on the nerves, that 
is, it neither causes contraction nor sensation, when its ac- 
tion on the nerve is prolonged. 

4. The electric current alone can modify the excitability 
of a nerve, and even rapidly destroy it, when the current 
circulates in a certain direction, and can preserve or aug- 
ment the excitability, when passing in the opposite direc- 
tion. 

5. Lastly, of all irritating agents, the electric current is 
the only one which possesses, for a long space of time, the 
power of reviving the excitability of the nerve, when it has 
become very much enfeebled in respect to other stimu- 
lants. 

Analogy between the Electric and JVervoiis Forces. — These 
differences between the action which the electric current 
exercises on the nerves, and that of other irritants, evi- 
dently show that the first is more simple than the others. 
Hence arises the analogy between the nervous force and 
the electric current, which the earliest observers of galvan- 
ism faintly perceived. 

But ought we, from this analogy, to conclude that the 
nervous force is merely an electric current ? Let us be 
17 



258 NERVOUS FORCE. Lect. XIV. XV. 

cautious in assuming such an inference, which is too often 
adopted as one of the best demonstrated experimental 
truths. 

Let us, in the first place, inquire whether with the instru- 
ments, which physical science furnishes us, the electrical 
current can be discovered in the nerves of a living animal ? 
Can this current exist there, and if it does, would it be 
under the requisite conditions to be endowed with the cha- 
racters of the nervous force ? 

The muscular electric current, on which we have dwelt 
at some length in one of the preceding lectures, is shown, 
by experiment, to owe its origin to chemical actions going 
on in the muscles. We have seen that this current exists 
in the integrant parts of the muscles, as well as between the 
molecules of two bodies which enter into combination; that 
it circulates there without any regularity, and one might 
say that, as Ampere imagined, it took place in magnetizable 
bodies, and that it is only by an experimental arrangement 
that we can discover the presence of this current. We 
have also shown, that the nerves have no direct influence 
over the production of this current, and that their office is 
limited, in experiments on the muscular current, to that of 
a slightly conducting body, communicating with certain 
parts of the muscle. 

JVo Electric Current in the JSTerves. — It was important to 
search for the presence of an electric current in the nerves 
of a living animal. I shall refrain from noticing here all 
the experiments which have been undertaken with this 
object in view^and which have terminated in the announce- 
ment, at one time, that this current did exist — at another 
time that it did not exist. The most conscientious and 
best established conclusion is this : — In the present state of 
science, and with the means of experimenting which me at 



LeCT. XIV. XV. NO ELECTRIC CURRENT IN NERVES. 259 

present possess, no sign of the electric current is found in the 
nerves of living animals. 

Some persons have asserted, that steel needles introduced 
into the muscles perpendicularly to the direction of their 
fibres, become magnetic, especially at the moment when 
the muscles contract. From this it has been concluded, 
that there existed an electric current in the nerves, and that 
the circuit was established as in a spiral or an electro-dyna- 
mic cylinder. 

I have repeated these experiments, by introducing steel 
or iron needles into the muscles of living animals, and in 
all directions relative to their fibres. In order to convince 
myself of the magnetization of the needles, thus plunged 
into the muscles, I made use of those of a very good astatic 
system, and even of those of the sideroscope of Lebaillif. 
I never obtained an affirmative result. I placed the recently 
prepared thigh and leg of a frog, in the interior of a spiral 
of varnished copper wire, the extremities of which were 
connected with those of a second smaller one, in which 
there was a soft iron wire. I afterwards irritated the nerve 
of the frog, observing, at the same time, if an induced 
current transversed the spiral, and magnetized the iron 
wire. All my researches were fruitless. 

I likewise tried the effect of introducing into an exposed 
nerve of a living animal, the conductors of a very delicate 
galvanometer by two points, as far apart as possible. I 
operated upon animals under the influence of certain nar- 
cotic poisons, and I excited strong muscular contractions 
in them, at the moment when I placed the two wires of the 
galvanometer in the nerve ; but I must confess that, when- 
ever the experiment was well made, I never obtained evi- 
dent and constant traces of the electric current. 

At the school of Alfort I made, in conjunction with 
Longet, an experiment of this kind upon a horse. We 



260 NERVOUS FORCE. Lect. XIV. XV. 

employed a very delicate galvanometer ; the nerve was ex- 
posed for a considerable extent of its course, and I could 
traverse it with the platinum extremities of the galvano- 
meter, by passing from a distance of 2 or 3 centimetres to 
that of 15 or 20. We never obtained distinct signs of the 
derived current, and in a constant direction, even w^hen the 
muscles of the animal were violently contracted. 

Lastly, I may add that, from what we know of the pro- 
perties of electricity, and of the laws of its propagation, it 
is impossible to conceive the existence of a current circu- 
lating in the nerves. In order that an electrical current 
should pass from one extremity of the nervous system to 
the other, it would be necessary to compare the nerve to 
a metallic wire varnished or otherwise insulated, an as- 
sumption which is not in accordance with fact. An elec- 
tric current which, subjected to the will, w^ould set out from 
the brain to reach the muscles, by traversing the nerves, 
could not be stopped in its course by the ligature of the 
nerve ; w^hereas, we well know, that the propagation of the 
nervous force is prevented by that proceeding. Lastly, its 
circulation in the nerves requires that the nervous system 
should form a closed circuit ; but the labours of anatomists 
are very far from having proved such an arrangement, espe- 
cially in the ultimate ramifications in the muscles, where it 
would be especially necessary. 

I have often tried an experiment, w^hich, had it given 
me a positive result, w^ould have proved, in an indirect 
manner, that the nervous system forms a complete chain 
for the electric current. I exposed a nerve in a living ani- 
mal at two distinct parts of its course, namely, at the top 
of the thigh, and at the lower extremity of the leg. I in- 
troduced the latter into a spiral, similar to that w^hich I 
described a few minutes ago, and which put into commu- 
nication with a second much smaller spiral, containing within 



LeCT. XIV. XV. NOT ELECTRICITY. 261 

it a soft iron cylinder. Through the nerve, thus prepared, 
I passed the electric current but never observed constant 
signs of the induced current in the spiral, which would 
certainly have occurred if the current had traversed this 
species of spiral w^hich, it is presumed, is formed by the 
nervous ramifications distributed over the muscles. 

Let us conclude, then, that the electric current does not 
naturally exist in the nerves of a living animal. The laws 
of its propagation require conditions which are not found 
fulfilled in the nervous system ; the propagation of its force 
is interrupted by causes which could not produce a similar 
effect upon the electric current. 

Relations between the JYervous Force and Electricity. — 
This unknown force of the nervous system is, therefore, 
not electricity, and still less is it the electric current. But 
what connexion exists between it and electricity, or the 
electrical current ? 

In order to reply to these questions, I will here sum up, 
in a few words, the only positive result that my lengthened 
investigations of electro-physiological phenomena of ani- 
mals have permitted me to deduce. 

There exists, between electricity and the nervous force, 
an analogy w^hich, if it does not possess the same degree 
of evidence, is, however, of the same kind as those ana- 
logies which we know to exist between caloric, light, and 
electricity. We have seen, when speaking of the pheno- 
mena presented by electrical fishes, that the faculty w^hich 
they possess of producing electricity is obedient to the 
nervous system. There is, then, in these animals a pecu- 
liar organic structure, such an arrangement of parts that, 
by an act of the nervous force they can develop the elec- 
trical fluid. You remember the identity of causes and cir- 
cumstances which excite and modify muscular contractions, 
and, this function is proper to these animals. You have 



262 NERVOUS FORCE. Lect. XIV. XV. 

seen, that in them the property which they have of giving 
the discharge is under the immediate dependence of the 
functions of the nervous system, as well, also, as is the 
faculty which the muscles have of contracting.* 

A crystal of tourmaline, when heated, develops electri- 
city, and from this fact we assume, that between caloric 
and electricity there exists a more or less intimate relation. 
The phenomena which we have observed in electrical 
fishes, prove that a link of the same nature unites the 
nervous force and electricity. Electricity is not the nervous 
force, nor is caloric electricity. The latter is derived from 
caloric in consequence of the form of the integral mole- 
cules of the tourmaline ; the nervous force is transformed 
into electricity under the influence of the peculiar structure 
of the organs of the electric fishes. 

How does Electricity excite JVervous Phenomena. — Let us 
examine, lastly, how electricity can excite nervous phe- 
nomena. The excitability of the nerves can also be 
awakened, and sensations and muscular movements deter- 
mined, by other agents as well as by electricity ; namely, 
by heat, mechanical and chemical actions. Ought we to 
conclude from these facts, that mechanical, chemical, and 
calorific action, affect the nerves after they have been trans- 
formed into the electric current ? We have no evidence 
in favour of such an hypothesis ; if, however, notwith- 
standing this, we would assume an analogous change, there 
would perhaps be some appearance of probability of it in 
the case of chemical actions ; but none for mechanical and 
calorific actions. There are no circumstances, in fact, un- 

* Mr. Grove {On the Correlation of the Physical Forces^ p. 49, 1846») 
has suggested, that "muscular force, animal and vegetable heat, &c.» 
might, and at some time will, be shown to have similar definite correla- 
tions" to those which he has shown to exist between the forces of the in- 
organic world. 



LeCT. IVX. XV. INDUCED CONTRACTIONS. 263 

der which we obtain a current by merely dividing a body. 
It is impossible to establish a comparison between a muscle 
and a thermo-electric body. In all these actions we can 
only see various causes of molecular movement. 

We, may, however, ask ourselves this question, — Does 
the cause of nervous phenomena reside in these molecular 
movements of the substance of the nerves, or is it owing 
to a disturbance in the equilibrium of the ether, distri- 
buted in the nerves ? Is this disturbance the consequence 
of a particular movement of the ether, which should con- 
stitute what we call the nervous fluid ? 

We can make no satisfactory reply to these important 
questions ; the facts which are necessary to enable us to 
resolve them are wanting, and will remain so, perhaps, 
for a long time to come. Yet. if it be sometimes allow- 
able, in scientific matters, to express, not only convic- 
tions, but even doubts, I will not hesitate to tell you that 
I do not consider it impossible to interpret nervous phe- 
nomena, by the mere movement of the ponderable mole- 
cules of nerves. 

But rather than stop to develop hypotheses, I believe it 
w^ill be more useful, before leaving the subject of the nervous 
force, to dwell for some time upon two classes of phenomena, 
or of the researches connected therewith. One relates to 
the fact which I discovered, and named contraction by in- 
duction, or induced contraction; the other relates to the deve- 
lopment of the nervous force. 

Induced Contractions. — By the term contraction by in- 
duction, or induced contraction, has been expressed, in 
England, a physiological fact which I discovered some 
years ago. I shall henceforth employ this name, which has 
the advantage of expressing briefly the phenomenon, and 
of specifying in some respect its nature. 

I shall commence by briefly stating in what this pheno- 



264 NERVOUS FORCE. Lect. IVX. XV. 

menon consists, and by detailing the principal researches 
which I at first made to determine its laws. Having pre- 
pared a galvanoscopic frog, we place its nerve upon one or 

Fig. 20. 




Experiment illustrative of [nduceJ Contraction. 

both thighs of a frog placed [prepared ?] in the ordinary 
manner : then, by applying the two poles of a pile to the 
lumbar plexus of this frog, we observe that when the 
muscles of the thighs contract, convulsions simultaneously 
occur in the galvanoscopic claw, whose nerve rests upon 
the thighs in contraction. 

I have also ascertained, that this phenomenon likewise 
occurs when w^e place the nerve of the galvanoscopic frog 
upon the muscles of the thigh of a rabbit, and make these 
contract by means of a current acting upon the nerve which 
ramifies in the thigh. I have also observed contractions of 
the galvanoscopic frog, without the employment of the 
electric current to excite the contractions of the muscle, 
producing the induced contraction ; the action of some other 



Lect. XIV. XV. CONCLUSIONS. 265 

stimulant, applied to the spinal marrow, or the lumbar 
plexuses, being substituted. 

Lastly, I have repeated these experiments by placing 
very fine layers of different substances between the nerve 
of the galvanoscopic frog and the muscular surface where 
the induced contraction is developed. A leaf of gold, or a 
very thin and insulating lamina of mica, or glazed paper, 
being interposed, prevents the production of the phenome- 
non ; that is to say, the contractions by induction do not 
occur in the galvanoscopic frog; but, on the contrary, a leaf 
of fine paper, moistened with water, does not prevent the 
occurrence of this contraction. 

Conclusions. — From the whole of these facts we are 
authorized to conclude, 

1st. That we cannot consider the induced contractions 
of the galvanoscopic frog, to be due to the electric current. 

2d. And that we might, on the contrary, assume, that an 
electric discharge happens during the contraction of the 
muscle. 

I have tried a great number of experiments with the view 
of supporting, by facts, this explanation of induced contrac- 
tions. With this aim, I formed a pile of entire frogs, and 
closed the circuit with the two extremities of the galvano- 
meter. When the needle had become stationary, I touched 
the nerve of the frogs, with a solution of potash, in order 
to excite contractions. By operating in this manner I have 
often seen the deviation of the needle increase several de- 
grees, and afterwards return to 0°. When the frogs had 
been touched several times with potash, or were so weak- 
ened that, on submitting them again to the stimulating ac- 
tion of the alkali, no more contractions ensued, it usually 
happened that no further deviation of the needle could be 
obtained. 

Finally, by moistening the nerves of frogs arranged in a 



266 NERVOUS SYSTEM. Lect. XIV. XV. 

pile, with acid or saline solutions, the deviation of the 
needle not only did not increase, but rapidly diminished. 

These facts, on which I have dwelt at some length, would 
appear at first sight favourable to the idea, that contractions 
by induction are the effect of an electric discharge which 
accompanies the act of muscular contraction ; nevertheless, 
I did not venture to affirm, from the outset, that the ques- 
tion was completely solved. 

Moreover, the phenomenon of induced contraction, has 
always appeared to me as being of very great importance ; 
and I could not therefore, resist entering into a complete 
investigation of it. I have latterly studied it with all pos- 
sible attention, and I believe, with some success. I hope, 
on account of the interest which this subject presents, you 
will excuse the minuteness with which I shall detail to you 
my numerous experiments. 

Before proceeding to new researches on the fundamental 
fact of induced contraction, I wished to re-examine and vary 
the experiments of which I have already given a sketch, 
and which I had made with the view of discovering whether 
electricity was developed during the contraction of a muscle. 
It was necessary, therefore, to operate with piles formed of 
a greater number of elements than those which I had pre- 
viously employed, in order to obtain a constant and a 
greater deviation ; consequently, I believed that a muscular 
pile was more suitable than one of frogs. 

The Muscular more Energetic than the Proper Current. — 
Since my recent experiments, there can no longer be a 
doubt, that with an equal number of elements, taken from 
the same frogs, the muscular current is more energetic than 
the proper current. I have lately shown that when by 
defective nutrition, by the effect of a very low temperature, 
or by the action of sulphuretted hydrogen, the muscular 
and proper currents are weakened in the frog, the diminu- 



LeCT. XIV. XV. MUSCULAR MORE ENERGETIC. 267 

tion is greater for the second than for the first; indeed, w-hen 
forming a pile with half- frogs, prepared by cutting the thighs 
in halves, I found a differential current more or less con- 
siderable, but always in the direction of the muscular 
current. It is only with very lively frogs, by dividing the 
thigh very high up, and by leaving only a small part of the 
surface of the interior of the muscle exposed, that we find 
no sign of the differential current, or, that it exists, in the 
direction of the proper current. Such was the fact which 
I discovered in my first experiments, and which, since my 
more recent ones, I can explain in a more satisfactory 
manner, by considering that in leaving the thigh nearly 
entire, we have two elements, namely, the muscles of the 
leg and those of the thigh, which give a current in the same 
direction ; whilst the muscular element which furnished the 
current in the contrary direction is a single one. 

Is Electricity evolved during Contraction ? — To return to 
our principal subject, I may observe, that I have employed 
a muscular pile in order to ascertain whether there was a 
development of electricity during the contraction of a mus- 
cle. But seeing that in order to excite the latter I was 
compelled to moisten the muscles with acid, saline, or, 
better still, alkaline solutions, I thought it right first to 
direct my attention to the action of these liquids on the 
muscular current. 

With this object I took eight frogs from among a very 
great number, and prepared them in the usual manner, by 
making with them sixteen elements, or half-thighs. I 
closed the circuit; the needle oscillated to 90°, and stopped 
at 22°. I formed another similar pile, but with this differ- 
ence, that I washed the half-thighs several times in pure 
water, and afterwards dried them: I obtained the same 
result. Sixteen other elements like the latter w^ere put, for 
some seconds, in a w^eak solution of sulphuric acid, then 



268 NERVOUS FORCE. Lect. XIV. XV. 

washed repeatedly until they no longer reddened the tinc- 
ture of litmus. The pile being formed, and the circuit 
completed, the direction of the current obtained was that 
of the muscular current, but only from 6° to 7° at the first 
deviation, and the needle stopped at 0°. I rapidly divided 
the half thighs with scissors, in order to renew the internal 
surface of the muscle ; and the pile, thus renewed, gave 
rise to one first deviation, which was also weaker than that 
before indicated. 

Being induced to think that the effects of the acid solu- 
tion upon the muscular elements, had been that of diminish- 
ing the conducting power, I made a muscular pile with 
eight half thighs taken from untouched frogs, to which 
halves I added four thighs taken from others also untouched. 
I obtained a current of 46°. Instead of employing four 
entire frogs, I used four also entire, but which had been 
plunged in sulphuric acid, and then washed: the current 
was 44P. The conducting power had not, therefore, been 
modified in the muscular masses which had been subjected 
to the acid solution. 

In order to have more absolute certainty of the accuracy 
of this result, I made the experiment, which I am about to 
describe, by using, in order to prolong the current, not 
entire thighs but eight halves of thighs, washed with the 
acid solution, and which I then had re-united upon their in- 
ternal surfaces in such a manner as to form a pile altogether 
similar to the preceding: the result was the same. 

I likewise repeated this experiment, by using a concen- 
trated solution of potash, in order to immerse for a few 
instants the muscular elements, or the half-thighs ; the latter 
were then washed in pure water, in order to remove every 
trace of alkali. With the pile, thus formed, of sixteen 
elements, and the circuit being closed, I obtained a current 
of 10° to 12° in the direction of the muscular current, and 



LeCT. XIV. XV. IS ELECTRICITY EVOLVED ? 269 

a definite, not appreciable, deviation, I renewed the in- 
terior of the muscle and recomposed the pile ; but the 
result did not vary. In this case, also, the conducting 
power had not changed. Consequently, acid and alkaline 
solutions acted, as I had found water to act when at a high 
temperature. 

I made another experiment of this kind, which I relate 
merely to show you that it accords perfectly with those 
before mentioned. Sixteen half- thighs were left for some 
seconds in water at -f 50° centig. [ = 122° Fahr.]. These 
elements w^ere then withdrawn from the water, washed in 
cold water, and formed into a pile, the circuit of which I 
completed, and obtained 12° at the first deviation, in the 
direction of the muscular current, and afterwards the needle 
■ stopped at 0°. The pile was re-formed, the internal surfaces 
of the muscles renewed, and the signs of the current were 
exactly the same as those w'hich I had at first obtained. In 
this case, also, I am convinced that the conducting power 
was not sensibly modified by the action of the warm water. 

I may add, also, that the muscular current is not dimi- 
nished by repeatedly w^ashing the muscles in pure water, at 
the ordinary temperature. I have many times observed the 
same deviation, sometimes a trifle stronger, sometimes a 
trifle weaker, by means of a pile of a certain number of 
elements, or halves of thighs, washed or not washed in pure 
w^ater. 

This experiment confutes Liebig's hypothesis relative to 
the muscular current. 

A very concentrated solution of common salt, into which 
the muscular elements are plunged for a few seconds, equally 
diminishes, in a very perceptible manner, the signs of the 
current. Thus, whilst sixteen ordinary elements give a 
first deviation which may amount to 90°, and a definite one 
of 20° to 22°, we obtain, on the contrary, if the elements 



270 NERVOUS FORCE. Lect. XIV. XV. 

have been plunged into a solution of common salt, and 
afterwards washed, a deviation of about 60*^ only at first, 
and afterwards the needle stops at 8° or 10^. We shall 
remark the agreement between this result and that to which 
Dumas has recently arrived, when investigating the in- 
fluence of certain salts on the arterialization of the blood. 

We are, then, led to conclude, that the efTect of these 
alkaline, acid, or very concentrated saline solutions, is to 
destroy in the muscular elements those conditions necessary 
to the development of electricity. This conclusion is in 
no way opposed to the origin we have assigned to this 
current. But since, by the action of acid or alkaline solu- 
tions, the signs of the muscular current either cease, or are 
very much weakened, it remains for us to explain how, in 
the preceding experiments, there has been no diminution of 
the current in a pile of entire frogs, when these have been 
touched at certain points with alkaline solutions, while it is 
immediately manifested when they are washed in an acid 
solution. In fact, you have remarked that, when we em- 
ploy alkali, there is, in many instances, a remarkable aug- 
mentation of deviation, although of short duration, in the 
first contractions excited. With acids, on the contrary, the 
deviation immediately diminishes, but appears again sojiie 
instants after. 

Let us endeavour to give an account of these phenomena- 
But first, I should describe the experiments which I have 
made in a most careful manner, with the view of discovering 
if there be a development of electricity during muscular 
contraction. 

I prepare several frogs according to the usual manner of 
Galvani. I then remove their legs, disjointing them with 
the greatest care. I have, thus, two thighs of a frog, united 
to a portion of the spinal marrow; I cut one of the thighs 
in half, and prepare, in the same manner, a certain number 



LeCT. XIV. XV. IS ELECTRICITY EVOLVED ? 271 

of elements all alike, and formed of an entire thigh, of a 
portion of spinal marrow, and of a half- thigh. You can 
easily understand how I compose a muscular pile with these 
elements, by applying the external part of the entire thigh 
to the internal part of the divided thigh of the following 
element. Afterwards I plunge the two extremities of the 
galvanometer into the liquid, in which the two extremities 
of the pile terminate. By means of a slight modification in 
the two extremities of the galvanometer, I have no occasion 
to hold them with the hands in order to keep the circuit 
closed. 

I have repeated this experiment many times, by employ- 
ing piles of a dozen, sixteen, or twenty elements. The first 
deviation, as well as the permanent one, is sometimes 
weaker than that obtained with piles composed of a like 
number of half-thighs. This difference must be ascribed 
principally to the greater length and resistance ofJered by 
the circuit. In all these cases, after having allowed the 
needle to become stationary, indicating a deviation which, 
in my different experiments, varied from 10^ to 12° or 15°, 
I rapidly touch the lumbar plexus of the elements of the 
pile with a concentrated solution of potash ; excepting, 
however, the two last, lest the solution should reach the 
liquid in which the extremities of the galvanometer are 
plunged. The muscular contractions became manifest after 
the application of the alkali, and continued for some instants, 
without scarcely ever being sufficiently strong to destroy 
the contact, by separating the elements from each other. 
During these contractions, if the experiment be made without 
any interruption or change in the circuit, the needle of the 
galvanometer undergoes no variation. 

In some cases, however, I have seen the needle descend, 
in others augment, 2° or 3°, but these variations are un- 
certain ; they are wanting in the greater number of cases, 



272 NERVOUS SYSTEM. Lect. XIV. XV. 

and are almost always due to some too brusque movements 
in the elements, in consequence of which the contacts are 
deranged. 

We therefore conclude, that direct experiment replies 
negatively to the question which we put whether there w^as 
a development of electricity during muscular contraction. 

There now remains to be explained the phenomena pre- 
sented by the proper current, when W'e employ entire frogs, 
and which consist of the almost constant occurrence of signs 
of augmentation, when we, for the first time, touch the 
lumbar plexuses of the frogs with potash ; whereas, on the 
contrary, when we apply an acid solution to them, the needle 
immediately descends. I have repeated and varied for this 
purpose my first experiments, and the following is the way 
in which these differences may be explained. 

Whatever be the form of the muscular elements which 
we use to make the pile, that is, whether they be made 
with entire frogs, with half-thighs, or such as we have de- 
scribed, when we moisten the surface of the muscular ele- 
ments with an acid, or alkaline solution, it invariably 
happens, whether there be or be not contractions, that the 
deviation diminishes, and that the needle returns to 0°, 
where it stops, if either the application of the alkali be re- 
peated, or the solution employed be too concentrated. 

This effect is analogous to that already described, and 
which the muscular elements present when they have been 
plunged for a few seconds into acid, or alkaline solutions. 

In our mode of experimenting, we excite the contractions 
in the muscles by touching with alkali those points which 
are out of the circuit, and which do not constitute parts of 
the electromotive element. 

In piles formed of entire frogs, with which we most fre- 
quently succeed in obtaining, in a transient manner, signs 
of augmentation in the current, by touching the lumbar 



LeCT. XIV. XV. IS ELECTRICITY EVOLVED ? 273 

plexus alone with alkali, we touch with alkali the parts 
which really constitute the electromotive element, and even 
in these cases we never succeed in obtaining the signs of 
the current, if we raoiwSten the whole of the muscular sur- 
face. 

I may also add, that if we employ an acid solution, taking 
care to touch with a pencil the lumbar plexus only, and not 
the muscles of the thighs or of the legs, the deviation is not 
weakened ; and notwithstanding the contractions excited, 
are less strong than those produced by the alkali, there is 
no augmentation of deviation. In order to cause the needle 
to descend, it is necessary to touch the surface of the 
muscles with an acid. This same effect takes place with 
the alkali, and it is, I repeat, in accordance with the ex- 
periments, already related, upon the muscular elements 
which have been immersed in acid or alkaline solutions. 

It is, then, only with the pile of entire frogs, or by 
touching with alkali the lumbar plexuses alone, that we 
often obtain a slight augmentation of deviation ; and this 
phenomenon appears when operating in the same manner 
with acids. By taking into consideration all the experi- 
ments which I have mentioned, this result cannot be re- 
garded as contrary to the negative reply that we have given» 
in an absolute manner, to the question of the development 
of electricity during muscular contraction. 

However little may have been the attention paid to the 
exposition of all these facts, it is impossible not to perceive 
how great is the difficulty which we encounter when we 
attempt to explain, in the particular case alluded to, why 
the alkali produces an augmentation of deviation in the 
proper current of the pile formed of entire frogs. I am 
inclined to think that, as the alkali excites in the muscles 
stronger and more permanent contractions than those pro- 
duced by acidsj the contractions ought in most cases to 
18 



274 NERVOUS FORCE. Lect. XIV. XV. 

rentier the contacts between the elements more perfect, and, 
consequently, the interior conducting power of the pile, 
ought to be augmented. Indeed, in the pile formed of en- 
tire frogs, the contact between the elements is always im- 
perfectly established, and we constantly observe great dif- 
ferences in the intensity of the current produced by these 
same elements, according to the greater or less care with 
which they are arranged. 

Whatever may be the explanation given of the slight 
augmentation manifested in the intensity of the proper cur- 
rent, by touching the lumbar plexus of frogs with alkali, 
and thereby exciting muscular contraction, it is certain that 
this fact alone cannot prove that electricity is developed 
during the muscular current ; the more so, as those before 
mentioned lead us to the conclusion that this development 
does not occur. 

Experiments on Induced Contractions. — I pass now to the 
exposition of the new and numerous experiments made 
upon the phenomenon of induced contractions. However 
extended, I do not think that I ought to pass them over 
in silence, on account of the great importance of the prin- 
cipal fact which they are designed to illustrate. 

It is sufficient to have seen once the phenomenon of 
induced contraction obtained without having excited the 
inducing contractions* by means of the electric current, to 
be convinced that this is not the direct cause of induced 
contractions. If, after having placed the nerve of the gal- 
vanoscopic frog upon the muscles of another prepared in 
the usual w^ay, we rapidly tear the spinal marrow of the 
latter, either with a pair of scissors, or a piece of glass, or 

* Henceforth I shall call, by way of analogy, the contraction indvcing 
or inducteous, in which the muscles are in contact with the nerve of the 
g.ilvanoscopic frog in which the induced contraction is developed. Note 
by Matteucci. 



LeCT. XIV. XV. INDUCED CONTRACTIONS. 275 

any other substance, it rarely happens that induced con- 
tractions are wanting. We are able to say as much of the 
induced contractions excited by a species of tetanus, which 
the frog suffers when it has been for a long time submitted 
to the passage of the inverse current at the time of opening 
the circuit. 

We must, therefore, confine ourselves to saying that the 
easiest method of observing the induced contraction is that 
of exciting the inducteous contraction by the passage of a 
current in the lumbar plexuses of the frog prepared in the 
ordinary manner. 

On this ground I have generally made use of the current 
to excite contractions in my experiments. I have taken 
every precaution to prevent the galvanoscopic frog, or the 
thighs of the inducteous frog, from carrying off a portion 
of the same current. The most sure method is that which 
consists in almost completely filling a common plate with 
turpentine, and placing the frog thereupon. It is needless 
to add that this substance should be sufficiently thick to 
prevent the frog from being submerged. Precaution also 
should be taken in preparing the galvanoscopic frog, to 
detach from the nerves all the muscular shreds, and to 
cleanse them thoroughly from blood, by means of blotting 
paper. 

Whatever be the arrangement of the nerve of the gal- 
vanoscopic frog, relatively to the muscular fibres of the in- 
ducteous thighs, the phenomenon of induced contraction is 
always manifested : thus, in some cases, I have stretched 
this nerve parallel to the fibres of the muscles ; in others I 
have arrranged them normally to these same fibres ; or, 
lastly, I have folded them zig-zag, and yet induced con- 
tractions have been constantly produced in every case 
without any perceptible differences. They are also obtained 



276 NERVOUS FORCE. Lect. XIV. XV. 

by disposing the nerve of the frog upon the gastrocnemius 
muscle of the leg. 

I have also tried the effect of washing the frog, in which 
I had excited the inducteous contractions, many times in 
pure water, in order to remove all traces of blood, or 
other secreted liquids, which might be on the surface of its 
muscles : and the induced contractions were still equally 
manifested. 

I removed with a razor, or better still, with scissors, a 
layer of muscular substance, and then placed the nerve of 
the galvanoscopic frog upon the internal surface of the mus- 
cles, and still obtained induced contraction. 

The same phenomenon is also produced by disposing 
the nerve of the galvanoscopic frog upon the muscle, in 
such a manner that the extremity of the nerve is folded 
upon the nerve itself, and forms a kind of closed circuit. 

I also endeavoured to satisfy myself w^hether these in- 
duced contractions would continue when the nerve of the 
galvanoscopic frog had not been cut. For this purpose I 
prepared a frog, taking care to preserve the integrity of the 
nerve, in the following way : after having skinned the ani- 
mal, I removed the abdominal viscera, then the bones 
and muscles of the pelvis, and lastly, those of the thigh, 
taking care to leave the nerve of the thigh entire. I then 
prepared another frog in the usual way, and placed it upon 
the turpentine, as already described. Afterw^ards I put the 
nerve of the galvanoscopic frog, thus prepared, upon the 
thighs of the second. By exciting muscular contractions 
in the latter, we obtained induced contractions like those 
when we employed the galvanoscopic frog ; and moreover^ 
we observed simultaneous contractions in the muscles of 
the back, and in the other leg. We shall have occasion 
hereafter to return to this experiment, and therefore,, 
for the present, we shall content ourselves with statingj, 



LeCT. XIV. XV. INDUCED CONTRACTIONS. 277 

that the induced contractions are also manifested when 
the nerve, placed upon the muscles in contraction, is un- 
touched. 

By using the frog, thus prepared, I have studied induced 
contractions, eraploying such an arrangement that the nerve 
which is in contact with the muscle in contraction is al- 
ready excited, either by a current or some other stimulant. 
For this purpose I either included the galvanoscopic frog 
in the circuit of a voltaic pair, or applied a drop of a very 
weak alkaline solution upon the nerve. Every time that 
the inducting muscles contracted, there was invariably in- 
duced contraction, whether the nerve by which this last 
was excited was previously irritated or not; and, conse- 
quently, when even the muscle on which this contraction 
took place was already contracted. Notwithstanding this 
contraction of the galvanoscopic frog, there is no diffi- 
culty in perceiving the induced contraction which ensues. 

Numerous experiments, equally simple, prove, that what- 
ever may be the manner in which the nerve of the induct- 
ing muscle be excited, if the contraction be absent, the 
induction is equally so. I shall confine myself to the rela- 
tion of some of the principal ones. If the nerves have 
been divided at two or three places in the inducting mus- 
cles, in order to prevent the contraction taking place, in- 
duction is constantly absent. 

If, without cutting the nerves, we make incisions into 
all the tendinous extremities of the muscles of the thigh, 
and if, moreover, we make some transverse incisions in the 
same muscles, avoiding the nervous cords, both the in- 
ducing and induced contractions are wanting. 

By carefully dividing all the muscles of the leg of a frog, 
we may expose the nervous filament which traverses it. 
If we irritate this nerve with either the current or any 
other stimulant, after having spread the nerve of the gal- 



278 NERVOUS FORCE. Lect. XIV. XV. 

vanoscopic frog upon the muscles of the thigh, when the 
latter suffers no contraction, induced contraction is also 
wanting. 

When experimenting upon rabbits and dogs, I have 
been able to operate with the electric current upon the 
nervous filaments distributed to the kidneys, stomach, and 
intestines ; the nerve of the galvanoscopic frog was, during 
the experiment, stretched upon these different organs, and 
in an analogous position to that which it had when it was 
placed upon the muscles. I never obtained any sign of 
induced contraction. 

I also sought to discover whether induced contraction 
occurred when the nerve of the galvanoscopic frog was 
placed on that which is irritated. For this purpose two 
galvanoscopic frogs were prepared, and the nerve of the 
first was placed upon that of the second, at points very 
near to the leg. In order not to omit any precaution in 
this experiment, we placed the two frogs upon turpentine, 
and afterwards irritated, either with the current or with 
some other stimulant, the upper parts of the nerve of the 
frog, which I shall continue to call inducteous. The 
galvanoscopic frog manifested no induced contractions ; 
whilst, on the contrary, it showed them immediately, if its 
nerve was disposed upon the gastrocnemius of the other 
frog. It is needless to add, that in making use of the cur- 
rent in order to excite the inducteous contraction, we must 
never put the conductors of the pile in contact or in proxi- 
mity with the nerve of the galvanoscopic frog. We may 
conclude from this experiment, that an irritated nerve, and 
within which the unknown principle which excites the con- 
traction in the muscle and the sensation in the brain is cer- 
tainly propagated, does not act upon the nerve of the 
galvanoscopic frog placed in contact with it. 

I will also relate the following experiment : I exposed 



LeCT. IVX. XV. INDUCED CONTRACTIONS. 279 

with all possible care the brain of a frog, prepared in the 
ordinary method, and spread upon this organ the nerve of 
the galvanoscopic frog. In several experiments made in 
this way, I applied, to the lumbar plexuses, sometimes the 
direct current sometimes the inverse one ; in others, I 
touched the plexuses with potash, and invariably obtained 
contractions in the inferior members, and convulsions of the 
back. Yet the galvanoscopic frog, whose nerve rested upon 
the brain, never manifested induced contractions. 

This same experiment has been tried, and with the like 
results, by applying the nerve of the galvanoscopic frog 
upon the spinal marrow, the brain, and different parts of 
dogs and rabbits : it is useless to say, that during the ex- 
periments, we irritated the animal in various parts, in order 
to be quite certain that the nervous action was propagated 
and reached the nervous centres. 

The induced contractions are, then, excited only by a 
muscle in contraction. 

I wished to examine whether these induced contractions 
became weakened, by provoking them by means of a mus- 
cle in which the contraction w^as also induced. In a word, 
I have sought for induced contraction of the first, second, 
and third order, &c. To do so, I prepared several galva- 
noscopic frogs, and one only in the ordinary way, I then 
arranged them in the following manner : — I spread the 
nerve of a galvanoscopic frog upon the muscles of the 
thighs of the entire frog ; then upon the muscles of the leg 
of the galvanoscopic frog, I spread the nerve of another 
galvanoscopic frog, and so on. The whole apparatus was 
placed upon turpentine. By exciting contractions in the 
whole frog, by means of the current passed through the 
lumbar plexuses, I frequently saw three galvanoscopic frogs 
contract at the same time, and nearly all of them with 
equal vivacity. This effect was constantly produced in 



280 NERVOUS FORCE. Lect. XIV. XV. 

two ; but I have never seen it in four. These, then, are 
induced contractions of the first, second, and third order. 

Before deducing from the facts which I have now made 
known, the conclusions which may be drawn from them, 
there remains for me to relate to you the numerous experi- 
ments which I have made, with the view of discovering 
what influence is exercised upon induced contraction, by 
bodies interposed between the contracting muscle and the 
nerve of the galvanoscopic frog. 

In my first experiments upon induced contractions, I had 
remarked that, by spreading a leaf of gold (such as is used 
for gilding) upon the inducting muscles, and afterwards 
placing upon one of the muscles, covered over with this 
small layer of gold, the nerve of the galvanoscopic frog, 
the induced contraction was no longer produced. In order 
to render this experiment successful, the muscle must be 
completely covered with gold ; and it does not succeed, 
after one or two contractions, by which the metallic leaf has 
become torn. 

I have also observed, that a leaf of glazed paper, placed 
between the muscle and the nerve, likewise prevented this 
same contraction. On the contrary, filtering paper, mois- 
tened with water, or with the serous liquid which moistens 
the surface of the muscles, when placed between this lat- 
ter and the nerve of the galvanoscopic frog, offers no 
obstacle to the production of these induced contractions. 

Our knowledge respecting the influence of interposed 
bodies on this phenomenon, was at first confined to the 
observation of these three facts. I have recently endea- 
voured to extend and vary the experiments. The mode of 
experimenting which I adopted, consists in preparing a 
frog, after the manner of Galvani, and placing it on turpen- 
tine ; at the same time an assistant prepared other galvano- 
scopic frogs, the nerves of which I placed upon the muscles 



LeCT. XIV. XV. INDUCED CONTRACTIONS. 281 

of the thighs of the first frog. I always used, in order to 
excite the contractions, a small pile of Faraday's of five 
elements immersed in pure water, and the conductors of 
which are varnished and covered with silk. 

No other liquid among the number with which I experi- 
mented, prevented the induced contraction from taking 
place. The liquids which I employed, and through which 
the phenomenon appeared, were water, slightly acidulated 
or salt water, serum, olive oil, diluted alcohol, resinous 
spirit varnish, and oil of turpentine. I generally let fall a 
few drops of the liquid I wished to try, upon the muscle, 
and I moistened with the same liquid the nerve of the gal- 
vanoscopic frog. The induced contraction was also pro- 
duced when we interposed a piece of filtering paper, dipped 
in the same liquid, between the muscle and the nerve. 

The slight conducting power of some of these liquids, 
such as oil, spirit of turpentine, varnish, &c., leads me to 
suspect that the induced contraction was not destroyed by 
the interposition of a perfectly insulating body. 

I have satisfied myself, in fact, that through even very 
thin layers of these liquids, the proper current and the 
muscular current are not propagated. It will be, doubtless, 
remembered, that when we take a galvanoscopic frog in 
the hand, and put its nerve in contact with moistened 
paper, which is in some way in communication with the 
ground, contractions are produced. The same phenomenon 
is observed by touching the muscles of a frog or other ani- 
mal, which communicates with the ground, with the nerve 
of the galvanoscopic frog. In all these cases, it is the 
proper current which circulates through the experimentor, 
the ground, the body touched, and the frogs; but if we 
plunge the nerve of the latter in oil, oil of turpentine or 
varnish, the slight layer of these liquids which remains 



282 NERVOUS FORCE. Lect. XIV. XV. 

adherent is sufficient to interrupt the circulation of the proper 
current. 

There is no doubt, then, that if the induced contraction 
be propagated through a layer of one of these badly con- 
ducting liquids, it is not owing to a current, which, taking 
its source in the contracting muscle, would be able to diffuse 
itself in the nerve of the galvanoscopic frog. 

Nevertheless, in considering the vast importance of these 
experiments for the theory of this phenomenon, I w^as 
anxious to try the effect of interposing between the muscle 
in contraction and the nerve of the galvanoscopic frog, a 
worse conductor than those just mentioned. The body 
which appeared to me fit for employment in these experi- 
ments, is the almost solid Venice turpentine, rendered more 
or less liquid by the addition of a small quantity of oil of 
turpentine. I varnished the thighs of a frog with this 
mixture, and placed some of it on the nerve of the galvano- 
scopic frog. After having arranged the experiment in the 
usual way, I found that the induced contraction continued. 

To demonstrate the non-conducting power of the mix- 
ture, I hasten to add, that if, in order to excite the contrac- 
tions, I applied one pole of the pile upon the insulating 
layer, well spread, without penetrating to the muscle itself, 
and with the other pole touched the leg of the galvano- 
scopic frog, no contraction was excited in the animal. 
These experiments evidently prove, therefore, that induced 
contractions exist through an insulating layer, capable of 
intercepting not only the proper or muscular currents, but 
even that of the pile which excites the inducing contrac- 
tion. 

If the insulating mixture exceed certain limits in its 
thickness, and if it have not a suitable degree of liquidity, 
the induced contraction does not occur. It is impossible, 
however, to state what degree of thickness and fluidity the 



LeCT. XIV. XV. INDUCED CONTRACTIONS. 283 

layer ought to possess to yield this result. It is sufficient 
for me to have fully shown that, in some circumstances, we 
obtained induced contraction when we have interposed, 
between the muscle and the nerve, an insulating layer, 
which certainly impedes the propagation of the proper, or 
muscular currents, as well as an ordinary voltaic current. 

Finally, I may state that I never succeeded in obtaining 
induced contraction, by interposing between the nerve and 
the muscle a solid body, whatever its nature and however 
slight its thickness might be. I have employed for this 
purpose very thin layers of mica, sulphate of lime, of gold, 
sized paper, and the leaves of plants, but the phenomenon 
was not produced with any of them. A very curious fact, 
and which, from its consequences, I believe to be important, 
is that of the existence of the induced contraction through 
the skin of the inducing muscles of the frog. This experi- 
ment constantly succeeds, whether the inducing contraction 
be excited by means of the electric current, or by any 
other stimulant applied to the lumbar plexus of the inducing 
frog. 

Hypotheses of Induced Contractions, — After having thus 
enumerated a long series of experiments relative to the cir- 
cumstances which intervene in producing, modifying, or 
destroying, the phenomenon of induced contraction, one 
would hope that, with such a collection of facts, it would 
be easy to give the physical theory of the phenomenon. 
Unfortunately, I believe that such is not possible, and this 
doubt obliges me to discuss minutely the different hypo- 
theses which can be formed to explain induced contrac- 
tions. 

Ist, It is sufficient to have once seen this phenomenon 
produced by provoking the inducing contractions with any 
mechanical stimulant, to be convinced that the electric 
current, employed to excite the contraction, is not propa- 



284 NERVOUS FORCE. Lect. XIV. XV' 

gated to the nerve of the frog, and takes no part in the 
phenomenon.* How can the induced contraction of the 
second and third order be understood? In what way can 
we explain the fact, that the induced contraction is wanting, 
even when the current has been, as usual, applied upon the 
lumbar plexuses, and that only because by the incision of the 
nerves in the thigh, we have abolished, or greatly diminished, 
the inducing contraction? Why does the induced contrac- 
tion fail when we apply the same current in the nerve 
below the thigh, in which case the muscles of the thigh do 
not contract? Why, when we operate with the current 
upon the lumbar plexuses of a frog, already weakened to 
such a degree that it only excites contractions at the com- 
mencement of the passage of the direct current, or at the 
moment of the interruption of the inverse one ; why, I say, 
is there, in this case alone, induced contraction ? It is use- 
less to continue to reconcile the objections we can make to 
the interpretations of this phenomenon, by having recourse 
to a diffusion of current to produce the inducing contrac- 
tions, a diffusion which we can in no way comprehend 
physically. 

2dly, We might suppose that the induced contraction is 
the effect of a mechanical stimulant, namely, of the contrac- 
tion of one of the inducing muscles, which thus gives a 
shock to the galvanoscopic frog. 

I have tried a great number of times, by using very sen- 
sitive galvanoscopic frogs, to excite, by all possible means, 
some movements in the muscles of the thighs, without 
causing the galvanoscopic frog to contract. If the true 

* From excessive precaution, I have often tried to obtain the induced 
contraction by exciting the inducing ones by lacerating the spinal marrow 
with a piece of glass. The induced contraction took place as if the in- 
ducing had been excited by the current or any other stimulant. Note by 
MatteuccL 



LeCT. XIV. XV. INDUCED CONTRACTIONS. 285 

cause of this phenomenon really resides in this shock, how 
can we explain the cessation of the induced contraction, 
occasioned by the interposition of a very thin leaf of gold, 
or mica, between the nerve and the muscle? I have very 
frequently tried the effect of applying the nerve of the gal- 
vanoscopic frog upon plates of metal or glass, upon tense 
membranes, and upon vibrating catgut strings, and have 
never seen contractions manifested in the galvanoscopic 
frog. It is not then the shock of the contracting muscle 
against the nerve of the galvanoscopic frog which is the 
cause of induced contraction. 

3dly, In some extremely rare cases contraction in the 
galvanoscopic frog is produced when we extend its nerve 
upon the thigh of the second frog, where both are perfectly 
insulated. But whenever this anomaly presents itself we 
never fail to discover the cause. It sometimes depends on 
some portion of the internal part of the muscle being ex- 
posed; sometimes on some portion of the muscle being left 
attached to the nerve of the galvanoscopic frog, and touching 
the nerve when we place it on the thigh. It appears to me, 
also, that these contractions are sometimes manifested when 
we touch the tendinous extremities, and the surface of the 
muscles of the thigh, with two points of the nerve of the 
galvanoscopic frog. I begin by telling you, that induced 
contraction is invariably obtained in all cases where, from 
all the precautions that have been taken, there exists no 
circumstances capable of exciting contraction in the gal- 
vanoscopic frog. We also know, that by dividing with 
scissors the muscular surface of the thighs, and rendering 
it by this means perfectly smooth, the contraction by in- 
duction takes place, when we apply the nerve of the gal- 
vanoscopic frog upon the fresh muscular surface. It is also 
produced through the skin of the frog, and even by placing 
layers of insulating liquids between the muscle and the 



286 NERVOUS FORCE. Lect. XIV. XV. 

nerve. And we have seen that the insulation produced by 
them was capable of intercepting the propagation of the 
proper or muscular currents. How can we suppose now, 
from these facts, that the induced contraction takes its origin 
from the circumstances which we have before enumerated, 
even by admitting that they are rendered stronger, or are 
excited, by the muscular contraction ? 

These circumstances can only arise from a phenomenon 
of the muscular or the proper current which ought to traverse 
the nerve of the galvanoscopic frcg, even when the latter is 
surrounded by a layer of an insulating substance, which we 
have seen cannot be the case. 

4thly, The first idea which presented itself, to explain 
induced contraction, was to admit that there was a develop- 
ment of electricity accompanying muscular contraction. 
There is a disengagement of heat during the contraction ; 
there may be eVen cases where light might accompany it, 
according to the observations of Quatrefages, observations 
which deserve, on account of their great importance, to be 
repeated in order to study more fully all their peculiarities. 

Hence, therefore, a certain degree of analogy would 
authorize us to regard as probable the production of electri- 
city during the muscular contraction. Moreover, the few 
experiments which I made when I discovered induced con- 
traction, would be equally explained, and in as satisfactory 
a manner, by this hypothesis. An insulating body, such as 
a leaf of mica, or glazed paper, prevents, by its interposi- 
tion, the induced contraction from taking place. The like 
result occurs when a leaf of gold, discharging perfectly the 
electricity which we presume is developed during contrac- 
tion, prevents the nerve from being traversed by it. 

Notwithstanding these first suppositions, which we made 
in the hope of being able to furnish a simple explanation of 
induced contraction, and at the same time a demonstration 



LeCT. XIV. XV. INDUCED CONTRACTIONS. 287 

of the existence of a very important fact respecting muscu- 
lar contraction, we are now compelled to abandon entirely 
this view, since it is disproved by experiment. 

At the commencement of this lecture, I related to you 
many experiments which I had made, with the view of 
ascertaining whether there was any augmentation in the 
energy of the muscular or the proper current during the 
act of contraction. All my efforts were useless, and I was 
obliged to conclude that experiment did not prove that the 
signs of the proper or muscular current acquired a further 
degree of intensity during muscular contraction. 

We might believe in the development of electricity in- 
dependently of the proper and muscular currents. But, 
how can we suppose such a fact, when we see that the in- 
duced contraction is transmitted through certain insulating 
substances, such as turpentine, oil, &c., whilst it no longer 
does so if we employ very thin leaves of mica. We might 
suspect that electricity, developed during muscular contrac- 
tion, acted by influence. In this hypothesis, we can under- 
stand why turpentine offered no obstacle to the passage of the 
contraction by induction; but the other fact, that with an 
extremely thin plate of mica, the same result does not 
happen, makes it become doubly inexplicable. I have 
tried the effect of covering a galvanoscopic frog, placed 
on a glass plate, with a plate of mica; the discharge from 
a Leyden bottle, passed between the knobs of the exitor 
upon the mica plate, and contractions were excited in the 
galvanoscopic frog. I shall not now stop to analyze this 
fact: it is sufficient for the present to show, that induced 
contraction through the mica ought to have occurred, if the 
cause of the phenomenon resided in an electric discharge, 
or was the result of the latter. I shall conclude by adding, 
that I have endeavoured repeatedly, but always unsuccess- 
fully, to excite contractions in the frog by holding the nerve 



NERVOUS FORCE. LeCT. XIV. XV. 

of the galvanoscopic frog in proximity with it, or even in 
contact with a metallic conductor traversed by an electric 
current. In order to find out the most favourable conditions, 
and in order that the circuit by induction should be formed 
and completed in the frog, I prepared the latter in such a 
manner that a long nervous filament, that is, one of the 
lumbar plexuses, and its prolongation in the thigh were 
exposed. The remaining portion of the body was left 
entire, and its two legs touched. I suspended the frog by 
silken cords, in an horizontal position, and its nervous 
filament being in contact and parallel with the voltaic 
conductor, which was varnished. When all these precau- 
tions are taken, in order that the frog may be perfectly in- 
sulated, we never observe contraction excited in the latter, 
at the commencement, at the opening, or at the closure of 
the circuit of the pile. It must be remarked, that in this 
experiment the circuit by induction may take place com- 
pletely in the frog. I employed Bunsen's pile of ten ele- 
ments, without obtaining any other result. 

From all this, it appears, that there is no experimental 
evidence in favour of the explanation of the phenomenon 
of induced contraction, by the assumption of the develop- 
ment of electricity during muscular contraction. 

We are, then, still ignorant of the cause of muscular con- 
traction, and all that we know of this phenomenon are the 
following particulars: it is produced, even when acting at 
great distances from the muscle, upon the nerve, whose 
ramifications it receives ; the integrity of the nervous fila- 
ment from the point where the excitation takes place to the 
muscle itself is indispensable; this transmission is eflfected 
with such rapidity, that we are compelled to compare it to 
that of electricity, light, and radiant caloric, propagating 
itself through various media ; what modifies, augments, or 
destroys the accomplishment of the chemical physico-phe- 



LkCT. XIV. XV. INDUCED CONTRACTIONS. 289 

nomena of the nutrition of the muscle, has an analogous 
action upon its contractibility, provoked by any influence 
acting upon the nerves ; and, lastly, in the laws of the con- 
traction of a muscle, we find an analogy with the physical 
laws of elasticity. 

The fact of induced contraction will, then, be a pheno- 
menon of induction of this unknown force, which circulates 
in the nerves and produces muscular contraction. 

By assuming as well-proved, that the phenomenon of in- 
duced contractions could not be satisfactorily explained by 
having recourse to the electric current, as T believe I have 
completely placed beyond doubt, it appears to me that we 
cannot, in speaking of a fact as simple as that of induced 
contraction, assume any other interpretation than that which 
we have given. The induced contraction will be a ne-w 
phenomenon of the nervous force, a phenomenon of w^hich 
we have already given the principal laws. To me it would 
seem most rational henceforth to call that muscular induction^ 
which we have hitherto termed induced contraction. 

A muscle in contraction exercises an inductive action 
upon a living nerve. After all, I am compelled to say that, 
recently, I have resumed the examination of the induced 
current, by considering it as due to a very feeble electric 
discharge analogous to that of the Leyden jar. After 
having seen that excessively feeble discharges produce 
contractions in frogs, knowing that the presence of these 
discharges cannot be detected either by the galvanometer 
or any other instrument, but only by the frog, it appeared 
worth while to ascertain whether a very slight discharge of 
the Leyden phial, traversing a muscle, acted on the nerve 
of the galvanoscopic frog, and under the same laws that 
we have found induced contraction to do. I must admit 
that, notwithstanding a great number of endeavours, I have 
not .been able to discover any differences. I wish, then, to 
19 



290 NERVOUS FORCE. Lect. XIV. XV. 

tell yoa frankly, that until new facts are obtained with re- 
gard to induced contraction, we cannot decide whether it 
be due to a nervous induction, or be the effect of an 
electric discharge occurring during contraction. 

If we could succeed by experiment in proving the truth of 
the latter hypothesis, we should have made a grand step in 
the analogies between muscular contraction and the elec- 
tric function of fishes. 

Production of JYervous Force. — In conclusion, let us say 
a few words on the production of the nervous force. Al- 
though it be true that we possess no knowledge of it ex- 
cept in living animals, and consequently, want the appara- 
tus to accumulate it and study its laws, out of the animal 
itself, yet we should not abandon all physical analogies in 
the investigations which we make relative to its mode of 
production. 

Whenever a movement occurs, or the effect of force is 
manifested, we are certain that some transformation of mat- 
ter must have taken place. Wherever a force is exerted, a 
chemical action precedes it. Caloric, electricity, and light, 
furnish us, at every instant, with evidence of this truth. 
But putting aside all analogies, let us examine the condi- 
tions under which the development, of what we call nervous 
force, takes place in animals. A man or animal, after a 
long walk, having put his machine into motion, is fatigued, 
arud needs repose and nourishment. Although it be true 
that facts are wanting to establish an intimate and really 
scientific connexion between the effects of labour, repose, 
and nourishment, on the one hand, and of the loss and 
reparation of the nervous force on the other, yet we can- 
not abstain from discussing these facts, complicated though 
they be, on the principles of mechanics and general phy- 
sics. 

Muscular exercise, of whatever kind, is constantly- fol- 



LeCT. XIV. XV. PRODUCTION OF NERVOUS FORCE. 291 

lowed by a loss of power, and as we see the animal machine 
recover its aptitude for exercise, after having obtained food 
and rest, we must admit that the force necessary to muscu- 
lar action may arise from the chemical actions of nutrition ; 
inasmuch as, by means of the latter, and of repose, this 
force is reproduced and accumulates in the nervous sys- 
tem. Interrupt for a certain time the sanguineous circula- 
tion in a muscle, and soon this becomes incapable of con- 
tracting; but with the return of blood the muscular force 
revives. In animals, where circulation and respiration are 
very active, the development of muscular force is more 
considerable. 

But among the numerous chemical actions that occur in 
animals, which is the one that gives rise to the force which 
is put in action during muscular contraction ? It is impos- 
sible to give a satisfactory answer to this question. 

Physiologists now admit that heat is produced by the 
combustion of fatty matters, and principally by that of 
bodies into which fecula is transformed during digestion : 
the nervous force may be due to chemical actions which 
take place during the changes which the neutral azotized 
substances of the tissues undergo. But I know of no ex- 
periment which directly proves this difference of origin, 
between heat and the nervous force. 

Of all chemical actions of which the animal is the seat, 
the only one which we perfectly know, and which we 
have even measured, is that which produces carbonic acid. 
On the average, man converts and exhales, in the form of 
carbonic acid, 10 to 15 grammes of carbon per hour. 

Setting out with these data, we shall endeavour to com- 
pare the nervous force which results from this chemical 
action, b^ representing the mechanical work done by a 
man in the space of one day, with the quantity of work that 
this same action could produce in the same space of time, 



292 NERVOUS FORCE. Lect. XIV. XV. 

either by means of heat, or by electricity developed by it. 
In other words, it is possible to ascertain whether we ob- 
tain with steam-engines, or electro-magnetic apparatus, 
and by means of a determined chemical action, a mecha- 
nical effect equal to, or different from, that which is pro- 
duced when this same action takes place within an animal. 

But before commencing this investigatio% I cannot re- 
frain from observing, that, in ordter to establish this com- 
parison, it is necessary to assume one of the two following 
hypothesis : we now know that heat, electrieity, and ner- 
vous force, are dseveloped in animals, and we assume that 
the causes of their production reside in the chemical ac-. 
tions of nutrition. But we may suppose that they are pro- 
duced in certain constant quantities, and independently 
one of the other; or, indeed, that from a certain chemi- 
cal action there never follows but a certain quantity of force, 
whatever be the form in which it is manifested. 

In order to make myself better understood, I will give 
an example : zinc burns irb oxygen, producing light and 
heat ; this same zinc can be oxydis^d by decomposing 
water and developing only heat, or heat and electricity, if 
we touch it with platinum wire. Suppose, now, that we 
could transform these forces into a certain quantity of me- 
chanical WQrk done by them, we might s^y that the sum of 
these quantities isthfr same in every case, and that when 
one happens to fail, the other is substituted: for it, by a 
relatjive- quantity dliawn from their mechanical equivalents. 
But it might equaJty happen, that they were developed in- 
dependently of each other. Expefiment would! ceply in 
favour of this latter opinion. I measured the heat disen- 
gaged by zinc oxydized by decomposing water, ajsd I re- 
peated this experiment by having, in. addition, ^the- disen- 
gagement of th.e electric cuEsent ; th© heat was invariably 



LeCT. XIV. XV. PRODUCTION OF NERVOUS FORCE. 293 

the same, and nearly equal to that which zinc produces 
when oxydizing by burning in oxygen. 

We might then consider all the chemical action of car- 
bon which combines with oxygen in animals, as the cause 
of nervous force, independently of the heat and electricity 
that it may produce ; and we would ask whether this ac- 
tion, taking place in the animal itself, determines an effect 
analogous to, or different from, that which it would deter- 
mine, if it occurred in a steam-engine or in an electro-mag- 
netic apparatus. 

While travelling on one occasion with the celebrated 
Robert Stephenson, we were obliged to send a man on foot 
forty miles. I asked Mr. Stephenson what quantity of car- 
bon was necessary to transport a man forty miles by a loco- 
motive. He replied, about 5 kilogrammes [about 11 lbs. 
avoirdupoise.] 

The person we had despatched accomphshed his journey, 
by w^alking, in less than ten hours, consuming by his respi- 
ration a quantity of carbon not exceeding 150 grammes, 
that is about ^'5 of the quantity which would have been ne- 
cessary if this transit had been effected by a locomotive. 
M. Dumas has calculated how much carbon would be 
burnt in a steam-engine, in conveying a man from the level 
of the sea to the summit of Mount Blanc. The quantity 
would be from 1000 to 1200 grammes ; but a man ac- 
complishes this feat by a two days' march, and consumes 
only 300 grammes. The difference in the second example 
is not so great as in the first ; because the useful result 
which we obtain from a stationary steam-engine, is much 
more considerable than that from a locomotive. It is 
equally true that the difference is very great, and that the 
work produced from nervous force derived from a certain 
chemical action, is much greater than that which this same 
action produces when converted into heat. 



294 NERVOUS FORCE. Lect. XIV. XV. 

I can show you in another way the great advantage 
which resuhs from the transformation of chemical action 
into nervous force in an animal. 

I endeavoured to measure the amount of mechanical 
work obtained, when applying to the nerves of a frog a' 
current produced during the oxydisation of a given quantity 
of zinc in a pile. Here are the numbers obtained : three 
milligrammes of zinc, oxydising in one day, furnish a cur- 
rent which, if we suppose that it could be continually ap- 
plied to the nerves of a frog, would produce a muscular 
power equal to 5*419 kilogrammes, raised to one metre in 
height during the same interval of time. It is probable that 
these numbers are far from being accurate, and I intend 
hereafter to repeat these experiments : it is, however, certain, 
that the causes of error are all one way, and tend to repre- 
sent as much smaller than it really is, the effect produced 
by the three milligrammes of zinc. 

The same quantity of zinc burnt, would yield a quantity 
of heat, which employed in forming steam, would execute 
work equivalent only to 0^, 8304, raised to one metre. 

Finally, the current produced by the three milligrammes 
of zinc was applied to an electro- magnetic machine ; and 
in this case we obtained 0^, 96, raised to one metre. 

Everything, then, leads us to the conclusion that the 
mechanical w^ork developed by chemical action, and trans- 
formed into nervous force, in an animal, is very great; and 
that in all the machines which man has invented he is al- 
ways, and wall perhaps for a long time to come, far from 
attaining that degree of perfection which exists in those ma- 
chines which we know not how to imitate and can only 
admire.* 

* In the Comptes Rendus for the 15th of March, 1847, Matteucci has 
drawn up the following summary of his hypothetical views respecting the 
nervous force : — 



LeCT. XIV. XV. PRODUCTION OF NERVOUS FORCE. 295 

1. The nervous fluid is produced by the chemical actions of nutrition. 

2. This fluid, developed principally in the muscles, is difiused there, and 
being endowed with a repulsive force between its parts, like the electric 
fluid, retains the elements of a muscular fibre in a state of repulsion analo- 
gous to that presented by electrified bodies. 

3. When this nervous fluid ceases to be free in the muscle, the elements 
of the muscular fibre mutually attract each other, as we see happens in 
cadaveric rigidity. 

4. This nervous fluid enters continually into the nerves, and from them 
passes to the brain, assuming in these bodies a new state which is no longer 
that of the free fluid: in this manner it passes from the muscle to the nerve. 
According to the quantity of this fluid which ceases to be free in the 
muscle, the contraction is more or less strong. 

5. This state is that of the nervous current, or species of discharge which 
proceeds from the nervous extremities to the brain, and returns in the con- 
trary direction, by the act of the will. 

6. When this discharge takes place, muscular contraction ought to take 
place, the fluid ceasing to be free in the muscles. 

7. This discharge of nervous fluid, acting as in the electric fish, ex- 
plains the induced contraction ; in both cases, and by the same disposition 
of parts, the nervous current produces a species of electric polarization of 
the elements, either of the muscular, or of the electric apparatus : the dif- 
ference of effects will be due to a different number of elements, to their 
dimensions, &c. 

8. The electric current impedes the nervous discharge, if it be directed 
in the contrary direction ; as in the direct current : the nervous fluid not 
being able to enter and accumulate in the nerve, this loses its excitability. 
The contrary takes place for the inverse current, which goes in the same 
direction as that of the nervous discharge : the nervous fluid is found ac^ 
cumulated in the nerve, and its excitability is augmented. — J. P. 



296 MUSCULAR CONTRACTION. LeCT. XVL 



LECTURE XVL 

MUSCULAR CONTRACTION. ANIMAL MECHANICS. 

Argument. — Muscular contraction : agents which affect it ; influence of 
the nervous force, velocity with which it is propagated. Analogy be- 
tween the structure of muscular fibres and of the electric organs of 
fishes. Phenomena of muscular contraction. Schwann^s observations 
on the degrees of muscular force evinced during contraction. Hypo- 
thesis of muscular contraction. 

Locomotion of animals. The locomotive organs may, in general, be re- 
duced to a system of levers. Discovery of the brothers, Weber, that the 
lower limbs oscillate during progression. Influence of atmospheric 
pressure on the coxo-femoral articulation. 

Passive organs of locomotion : composition and structure of bone. Rela- 
tion of the length and thickness of bones to their resisting power. 

Muscular power. Velocity and extent of motion, how gained. Borelli*s 
principles for estimating the force of muscles. The fore arm is a lever 
of the third kind. Standing on one foot is effected by a lever of the 
second kind. Estimated strength of the muscles of the fore arm. 

The essential part of the mechanism of locomotion is either elongation or 
shortening. 

In the preceding lecture we were engaged in giving an 
exposition of the laws of the nervous force, and in investi' 
gating the causes of its development ; as far, at least, as is 
allowable in a course of lectures, from which vague notions, 
and purely hypothetical deductions, have been carefully 
excluded. 

Muscular contraction and its result, locomotion, are the 
effects of the force which we have now to study ; and in 
treating of these subjects, we shall confine ourselves to that 
which is more positive, and best established. 



LeCT. XVI. HOW INDUCED. 297 

Muscular Contraction^ how induced. — Volition, mecha- 
nical actions, heatj and electricity, determine muscular con- 
traction by their action upon the nerves ; for this effect 
does not take place if the nerves be tied, or if their struc- 
ture be in any way altered. There is, then, evidently a 
force propagated along the nervous filament to the muscu- 
lar fibre. We are, likewise, compelled to admit, that the 
fibre possesses the aptitude for, and the property of, con- 
tracting under the action of the nervous force ; and we 
cannot explain why, for so long a time, there prevailed, 
and still prevail in physiology, theories, either exclusively 
ascribing the contraction of muscles to the action of the 
nervous force, and denying to the muscular fibre the power 
of contracting per se ; or ascertaining that the power of con- 
traction resides in the fibre and is independent of the ner- 
vous force. In the same manner, that elasticity is the pro- 
perty of bodies by means of which molecules are capable 
of being put into vibration ; so is it necessary that some 
impulses should be communicated to these molecules, in 
order to throw them into vibration. 

Velocity of the JYervous Force. — The velocity with which 
the nervous force is propagated is very great, and may be 
compared to that of light and electricity. I would ob- 
serve, however, that without being able to deny, that its 
velocity is as great as that of the two latter agents, we are 
in want of experiments to support this supposition. The 
distances to which we are accustomed to observe the ner- 
vous force propagated, are very short, and we ought not 
to be very much surprised at the velocity of its propaga- 
tion. 

When we observe a muscle at the moment of its con- 
traction, we soon perceive that its longitudinal fibres be- 
come shorter, and augment in diameter. Such is the 



298 



MUSCULAR CONTRACTION. 



Lect. XVI. 



result of the numerous observations of Fodera, Edwards, 
Weber, &c. 

Experiment shows that the volume of a muscle does 
not sensibly alter during contraction. This vessel contains 
a torpedo and a prepared frog ; it is filled with water, and 
closed with a cork perforated by a narrow tube, in w^hich 
the liquid rises. Two insulated, varnished wires pene- 
trate the vessel, and when brought into communication 

Fig. 2^1. 




Fragments of Striped Elementary Fibres, showing a cleavage in opposite direc- 
tions; magnified 300 diameters; 1, longitudinal cleavage; the longitudinal and trans- 
verse lines are both seen ; some longitudinal lines are darker and wider than the 
rest, and are not continuous from end to end ; this results from partial separation of 
the fibrillse; 6, fibrillse, separated from one another by violence at the broken end of 
the fibre, and marked by transverse lines equal in width to those on the fibre; 7, 8 
represent two appearances commonly presented by the separated single fibrillae, (more 
highly magnified ;) at 7 the borders and transverse lines are all perfectly rectilinear, 
and the included spaces perfectly rectangular; at 8 the borders are scalloped, the 
spaces bead like; when most distinct and definite, the fibriila presents the former of 
these appearances ; 2, transverse cleavage ; the longitudinal lines are scarcely visi- 
ble ; 3, incomplete fracture following the opposite surfaces of a disc, which stretches 
ncross the interval and retains the two fragments in connexion ; the edge and surface 
of this disc are seen to be minutely granular, the granules correspond in size to the 
thickness of the disc, and to the distance between the faint longitudinal lines; 4, an- 
other disc nearly detached; 5, detached disc more highly magnified, showing the sar- 
cous elements. 



with the poles of a pile, excite contractions both in the 
torpedo and frog ; but you perceive that no change has 



Lect. XVI. 



CONTRACTION PARTIAL. 



299 



Fig. 22. 



taken place in the height of the column of the liquid, 
which is precisely the same now, that it was before the 
contractions. 

Structure of Muscular Fibre. — According to the observa- 
tions of modern micogrophers, it appears, that muscular 
fibre is composed of a great number of cells or globules 
(discs) arranged in piles, according to the longitudinal di- 
rection of the fibres ; and that from the union of these 
piles muscular fasciculi are formed ; so that a muscle ap- 
pears to be susceptible of a kind of cleavage, 
both longitudinally and transversely. This 
structure has, therefore, a great analogy with 
that of the electric organs of fishes ; and it is 
very remarkable that, with respect to the gene- 
ral circumstances of the two phenomena, the 
same law^s preside over the discharge of elec- 
tric fishes and muscular contraction. 

In the act of contraction, the globules, or, 
to speak more accurately, the transverse striae 
of muscular fibres, approach one another ; the 
distances betw^een them diminish, and the 
thickness of the fibres augments : hence the 
volume of the muscle remains sensibly the 
same. 

Contraction partial. — Bownian states, that 
active contraction never occurs in the whole 
of an elementary muscular fibre at once ; but, ^''^cture of the 

/. ' ' ultimate fibrillsB of 

according to this skilful anatomist, the con- striated muscular 
traction is partial, and is propagated during ^'"■^=~°' ^ ^^"^ 

. , .,,. ®ina state of ordi- 

a certain very short, but yet appreciable inter- nary relaxation ;&, 
val of time ; so that in a fibre in a state of ^ *^'"''' '" ^ ^^*^« 

. , . of partial contrac- 

contraction, there must be some points at rest, tion. 
and others brought nearer together. 

I am inclined to think that these appearances exist only 



I 




1 


1 




1 


■ 




1 


■ 




1 


■ 




1 


■ 




1 


■ 




1 


■ 




1 
1 



300 MUSCULAR CONTRACTION. LeCT. XVI. 

in muscular fibres which are torn, and of which, conse- 
quently, one at least of their extremities is free. But, 
even according to Bowman's opinion, muscular contraction 
must determine the locomotion of a limb, for the inac- 
tive parts of the muscle, would be placed under the same 
circumstances as the tendinous extremities which are de- 
void of contractility. 

Power of Muscles at different Periods of Contraction. — 
Schwann has made some important researches on the va- 
riations of the muscular force, according to the different 
degrees of contraction of a muscle ; but I shall restrict 
myself to a notice of the principal result which he obtained. 
The force dis^played during contraction, is always propor- 
tional to the length of the muscle at the different periods 
of contraction : so that this force, which is very great in 
the beginning, when the contraction commences, dimi- 
nishes in proportion to tfce shortening of the muscle, and 
vanishes when the contraction has attaim^d its maximum. 
A muscle which contracts may, consequently, be compared 
to an elastic thread stretched by a weight, and which, when 
this is removed, resumes its primitive length with a force 
invariably proportional to the weight which it supported, 
and to the elastic elongation it had undergone. This re- 
sult is a refutation of the assumption, often made, that 
muscular contraction is due to the reciprocal attraction of 
the globules, or elementary paTticles which compose the 
muscular fibre. If this were true, the force exhibited by the 
muscle ought t© augment during contraction : on the con- 
trary, the result obtained by Schwann might be explained 
by saying, that contraction is produced by the instantane- 
ous cessation of a repulsion, assumed to exist between the 
discs, and excited the instant previously. 

Hypothesis of Muscular Contraction.— 1 take this opportu- 
nity of saying a few w-ords respecting an hypothesis w^hich 



LeCT. XVI. LOCOMOTION OF ANIMALS. 301 

has engaged my attention for some time, and which is sup- 
ported by a great number of facts and some well founded 
analogies. The contraction of a muscle may be assumed 
to consist, at first, in a repulsion existing between the ele- 
mentary parts of the muscular fibre for a very short period, 
and to which succeeds, in; virtue of its proper elasticity, the 
return of the fibre, or, as it is commonly said, the muscu- 
lar contraction. Nervous action would thus produce re- 
pulsion, whieh, by the dispersion, or instanteineous loss of 
this force,, must be followed by contraction. Fancy a 
string of globules, or discs, kept in their places by as many 
interposed springs ; an electric discharge communicated to 
this system produces, at first, repulsion between the glo- 
bules, assuming, that these only were capable of being elec- 
trified. The repulsion will go on augmenting in the 
direction of the^ globules situated at the two exiremilies of 
the string.. The electricity, being dissipated, the globules 
return to their natural position, which they will at first pass 
beyond by the action of the interposed springs. 

Locomotion of Animals. — I shall follow up these brief 
generalities on muscular contraction, by an exposition of 
the mechanism relating to the locomotion of animals. I do 
not propose, in the present course of lectures, to enter into 
a minute description of the various ways in, which this 
function is effected in the different parts of the body of an 
animal, and in different animals; but must confine myself 
to a few general principles, sufficient to prove that the 
theories of mechanics, prroperly so called, are the founda- 
tion of the apparatus, or organs of locomotion of animals. 

All the locomotive organs of animals may be in general 
reduced to a system of different kinds of levers, of which 
the length, the resistance, and the weight, are suitably com- 
bined; and to these levers are applied, in various ways, 
musG^^ar fascieuli. Air,, water, andi garth, are the media 



302 . MUSCULAR CONTRACTION. LeCT. XVI. 

where these movements take place; and which furnish fixed 
points, or points of support. The theories concerning the 
composition of forces, the centre of gravity, levers, and the 
resistance of media, necessarily apply, therefore, as well to 
animal machines, as to any machine employed in the arts. 
Oscillation of the Lower Extremities in Walldng. — We 
are indebted to the brothers, Weber, for an important dis- 
covery in the theory of walking and running in man, and 
of which 1 must not leave you ignorant. It consists in 
having demonstrated, by experiments, that the lower limbs, 
when put in motion, oscillate in a pendulum-like manner 
around the trunk, by the action of gravity. Limbs of dif- 
ferent lengths, both of living men aod of bodies, were made 
to oscillate; and in every case it was found that the dura- 
tions of these oscillations were proportional to the square 
roots of the lengths of the oscillating limbs. These move- 
ments, then, are effected independently of our will; a fact 
which explains the perfect regularity with which the steps 
succeed each other in a child as well as in an adult, in the 
idiot as well as in him whose will and sensibility have re- 
ceived full development. The action of the muscles, there- 
fore, is little or nothing in the execution of these movements. 
The leg raised and then left to itself, accomplishes the step 
by the sole influence of gravity. The head of the thigh- 
bone suffers a very slight friction only in rotating in the 
cotyloid cavity, where it is retained by atmospheric pressure, 
which thus assists in accompHshing these movements. The 
whole weight of the limb does not press against the sides 
of the hip-joint: the head of the thigh-bone remains fixed 
in this cavity by atmospheric pressure, and hence the effect 
of gravity upon the member is destroyed. For this fact 
we are indebted to the researches of the brothers, Weber, 
who have demonstrated this mode of action of atmospheric 
pressure. The tendons and the muscles which connect the 



LeCT. XVI. PASSIVE ORGANS OF LOCOMOTION. 303 

thighs to the trunk were cut across in a suspended subject, 
without the limb suffering the least change in its position ; 
but when a hole was made into the cotyloid cavity, the 
limb immediately fell, and it could be made to fall, or be 
prevented from doing so, merely by opening or keeping 
closed this aperture. By calculating the pressure exercised 
by the atmosphere against the plain section of the cotyloid 
cavity, we find that it is equivalent to 11-970 kilogrammes 
[about 26 lbs. 6 oz. avoirdupoise;] that is to say, it slight- 
ly exceeds the mean weight of the leg. 

Passive Organs of Locomotion. — The passive organs of 
locomotion, like every other part of the human machine, 
present a constant application of the principles of mechanics, 
in order to realize a very complicated result. Suppose we 
said to an engineer, we want a moveable column composed 
of a certain number of cylindrical pieces, united together 
by their extremities, and of which the length must be varia- 
ble: the thickness of the column should be such that it can 
support the weight with which it will be loaded, and it 
should be capable of resisting lateral shocks. The extremi- 
ties of the different pieces of the column shall so terminate, 
that the forces to put it in motion may be applied there; 
and, finally, the column must be capable of executing a 
great number of partial movements without deranging its 
simplicity and elegance. The engineer would certainly 
consider it a problem difficult, if not impossible, to solve. 

Bones.— 'Thti bones are formed of a mixture of gelatine, 
and of phosphate and carbonate of lime in different propor- 
tions. If these vary, great changes in the degree of tenacity 
and elasticity of the bones in consequence take place. 
Independently of their composition, the more or less fibrous, 
and more or less spongy, texture of bones, serve to modify 
their weight and resistance. These properties also vary 
according to the dimensions of the bones. Euler proved 



304 MUSCULAR CONTRACTION. LeCT. XVI. 

long since, that the weights, which cylindrical or prismatic 
rods can sustain without yielding, are in the inverse ratio 
to the square roots of their length, provided that their na- 
ture and section remain constant. If we express by 1, 2, 
3, 4, &c., the lengths of the homogeneous rods, the weights 
that they can support without bending are expressed by the 
numbers 1, ^, ^, j^^, &c. Hence, the bones must have dif- 
ferent lengths, according tothe different efforts which they 
are requiired to sustain. 

Salidie4 demonstrated long since,, that within certain limits 
of thickness of the osseous wall, the resistance which bones 
oppose to fracture,, against a force applied laterally, is 
greater in a hollow cylinder of large diameter than in a 
solid cylinder, and consequendy one of smaller diameter. 
All bones are constructed so as to give the necessary resist- 
ance, without greatly increasing the weight. 

Muscular Force. — Let us, in the last place, speak of 
muscular power, a subject, which I must admit is not more 
advanced now than it was a century ago, when Borelli 
began to stud'y it. In general; we observe that, in the 
employment of muscles in locomotion, their arrangement is 
so combined as to give the greatest possible velocity and 
extent of motion, without sacrificing the simplicity, harmony, 
and elegance of the oiffeEent parts of the human machine. 
In every possible case, the following conditions are united 
to realize these results : 

1st. The oblique insertion of the muscular fibres in the 
tendon. 

2d. The obliquity of the direction of the tendon to the 
axis to which it is attached, and on which it must act. 

3d. The proximity of the points of insertion of the 
tendons to the articulation of the bones, which serve as 
points of support. 

The prin/siples established by Borelli for calculating the 



LeCT. XVI. MUSCULAR FORCE. 305 

force of the different muscles of the same animal, and which 
principles are at the present time generally admitted, are as 
follows: — 

1st. Two muscles composed of the same number of 
fibres, and consequently of equal thickness, can raise a 
given weight to heights which are proportional to the 
lengths of the muscles ; or rather, they can raise to a given 
height weights which are proportional to their lengths. 

2d. If two muscles be of equal length, they can raise to 
a given height weights proportional to their thickness. In 
a word, the volume of a muscle determines the weight it 
can raise; and, on the contrary, the height to which the 
weight can be raised varies according to the length of the 
muscle. In more general terms, the mechanical work of a 
muscle varies according to its length and thickness. It is 
unnecessary to say that we omit mentioning here an element 
which is not susceptible of being measured a piiori, namely 
the intensity of the nervous force, which varies with the 
will. 

It is easy to understand how the extent of motion of the 
bone depends on the different obliquity with which the 
muscular fibres are inserted in the tendon, and how it must 
increase in proportion as the fibres aye the more obliquely 
attached. 

We may also observe that, according to the different 
obliquity with which the muscle is made to act upon the 
moveable bone, a greater or less loss of power must ensue. 

Such is the most general arrangement of the motor organs 
of animals, and we can readily conceive the reason, when 
we consider that the bodies of both man and animals gene- 
rally, would have a monstrous form if the muscles acted 
normally upon the bones. In order to diminish a portion 
of the loss of the force w^hich the muscles suffer in conse- 
quence of the obliquity of their insertion on the bones, the 
20 



306 MUSCULAR CONTRACTION. LeCT. XVI. 

latter terminate by spherical enlargements, and the tendons 
glide over these, in proceeding to attach themselves in- 
feriorly to the bone to be put in motion. 

Lastly, let us remark, that on the relative position of the 
points of support [fulcra or props,) and of the points of ap- 
plication of the resistance (or weight,) and of the power 
(or force) in the levers of the animal economy, depend the 
well-known relations between the spaces traversed by the 
power, and the resistance, and the absolute forces which 
they represent. In general, the levers of the human body 
are of the third kind, so that the arm of the lever of resist- 
ance surpasses that of the power. The fore-arm off'ers us 
an example of a lever of this kind ; indeed, its point of 
support is at the elbow-joint, its resistance is the weight of 
the arm, which we presume to be applied at its middle, and 
its power is the flexor muscles, fixed at the extremity of the 
bones of the fore-arm. We need only compare the relative 
points of application, of the power, and of the resistance, 
with the point of support, to obtain numbers expressing the 
ratios of the movements of the power and of the resistance, 
such as they are furnished by theory. The extremity of the 
fore-arm traverses an arc much greater than that described 
by the flexor muscles; the first accomplishes its movement 
with a velocity of 974 millimetres in the second ; the other, 
on the contrary, with a velocity of 81 centimetres. 

In cases where it is necessary to make an equilibrium to 
a greater force, by means of a smaller one, the lever of the 
second kind is employed ; we have an example of this in 
man, when standing on one foot, which thus supports the 
whole weight of the body. 

Borelli endeavoured to value the force of a great number 
of muscles, and deduced, from the numbers found in his 
experiments, the amount of force lost in most muscular 
movements, in order to obtain velocity. We shall notice 



LeCT. XVI. MUSCULAR FORCE. 3Cf7 

one only of the cases examined by Borelli; that being suffi- 
cient to explain his mode of calculating the forces of 
muscles. The weight of the fore-arm of man is about 2 
kilog., which we may consider as applied at the middle of 
the fore-arm ; or, what is the same thing, we may assume 
that this w^eight is 1 kilog., applied at twice the distance 
from the point of support, namely, the hand. It is known 
that a man can support with his extended arm a weight of 
about 13 kilog., and consequently the total resistance to 
which the equilibrium should be made is 14 kilog. But 
the poW'Cr of the muscles for the arm of the lever has a 
length which we know to be about the twentieth part of that 
of the fore-arm ; therefore, the value of x will be 280, or 
the product of 14 multiplied by 20, so that to carry a weight 
of 14 kilog. with the hand, the flexor muscles ought to 
make an effort equal to 280 kilogrammes. 

The generalities which we have now explained suffice 
to enable you to comprehend the mechanism of the different 
movements of animals. If I had wished to speak with all 
possible minuteness of the theory of walking, of running, 
of swimming, of flying, &c., the subject would have passed 
beyond the limits, not only of a single lecture, but even of 
an entire course. 

In all cases, whatever be the animal and the manner of 
its progression, the essential part of its mechanism of loco- 
motion invariably consists in an elongation or a contraction, 
movements which the two branches of the arc or arcs, 
formed by certain parts of the animal, execute. Under 
some circumstances, these arcs are formed by the body of 
the animal, which then becomes vermiform, or arched, as 
in animals which swim or crawl. In other cases the move- 
ments of extension and of flexion result from the successive 
approach and retirement which the tw^o sides of an angle 
formed by the limbs of the animal undergo. One of these 



308 MUSCULAR CONTRACTION. LeCT. XVI. 

sides always contains the point of support, or both of them, 
according to the medium in which the animal moves. Air, 
water, and the ground, offer resistance to the parts of an 
animal which strike against, or press upon, these media, 
and the movement is produced in the same way that the 
progression of steam-boats and of locomotives is effected, 
by the impulse of the paddles against the water, ^nd of the 
friction of the wheels upon the rails. 



LeCT. XVII. CIRCULATORY APPARATUS. 309: 



LECTURE XVII. 



CIRCULATION OF BLOOD. 



Argument, — Circulatory apparatus ; the heart ; blood vessels. Mechanism 
of the circulation. The blood ; its general properties ; quantity in the 
body. Number of pulsations. Velocity of the circulation; experiments 
of Hering, of Matteucci and Piria, of Poiseuille, and of Hales. Pressure 
on the blood in the vessels; Poiseuille's hsemo-dynamometer ; results 
obtained with it. Motion of the blood in the capillaries. Motive forces 
of the circulation ; muscular contraction of the heart; elastic contraction 
of the arteries. Pulmonary circulation. Concluding observations. 

One of the most important effects of the nervous force is 
the motion which it communicates to the blood in animals ; 
for it is now admitted by all physiologists that muscular 
contraction is the principal agent concerned in the circula- 
tion of the blood. In order to carry out the intentions of 
this course, I propose, in the present lecture, to demonstrate 
to you that the apparatus which puts the blood in motion, 
by muscular contraction, possesses all the conditions of an 
hydraulic instrument; and I trust that I shall be able to 
prove to you that the simplest and most elementary laws of 
the movements of liquids are applied, to obtain, by the 
passage of the blood through the various organs and dif- 
ferent parts of the body, the numerous effects necessary to 
the development and preservation of the animal. 

I regret that I am unable to treat of this subject in the 
extended manner which it deserves, in consequence of 



310 CIRCULATION OF BLOOD. LeCT. XVII.- 

being confined within the narrow limits which I feel obliged 
to impose on myself in these lectures. I shall, therefore, 
restrict myself to an exposition of those experimental results 
which are best established, and which are necessary for the 
theory of this function. 

Circulatory Apparatus. — The apparatus for the circula- 
tion of the blood may, in its simplest form, be reduced to 
a system of canals or tubes, forming a kind of complete 
circle, invested at some point with a muscular substance to 
develope the force necessary for putting the blood into 
motion. This apparatus becomes necessarily more com- 
plicated in proportion as we ascend in the scale of beings ; 
and, whilst, in the lower animals, the nutritive liquid fills 
a vast system of lacunae, w'hich constitutes the whole of 
their organization, and is endowed with a slow and irregular 
motion ; in the higher animals, on the contrary, the blood 
circulates in a system of canals of a peculiar organization, 
in a fixed direction, and with a constant, but more or less 
considerable rapidity. The apparatus is complete when, 
for the execution of this function, two orders of vessels are 
employed whose structure is very different, and which com- 
municate with each other after having divided into a great 
number of ramifications of a constantly decreasing diameter. 
In one order of vessels the blood travels from the great 
trunks towards the smaller ones; and in the other it moves 
in an opposite direction. At the point w^here these two 
systems arise there is a peculiar organ called the heart. 
The small tubes which altogether form the extremities of 
the arteries and the veins, are called capillary vessels. And 
as these two orders of tubes terminate by the opposed ex- 
tremity in the cavities of the heart, the vascular apparatus 
may be correctly said to form a complete circle, which the 
blood traverses, returning incessantly to its starting point. 

I cannot pass over in silence various particulars relating 



LeCT. XVII. HEART. 311 

to the structure of the circulatory apparatus; but I shall 
notice them in the briefest manner possible; and as we 
ought to study the function in its most perfect and compli- 
cated state, the few anatomical points which I shall here 
notice will relate to the human body. 

Heart. — The heart of man is a conical or pyramidal 
cavity, formed by a kind of muscular sac divided into two 
parts, each composed of two cavities, placed one above the 
other ; one of these is called the ventricle^ the other the 
auricle. The two ventricles of the heart occupy the lower 
portion ; and their cavities are much larger than those of the 
auricles placed above them. The left auricle and ventricle 
belong to the apparatus for the circulation of arterial blood • 
while the right auricle and ventricle belong to that for 
venous blood. The ventricles have thicker walls than the 
auricles, especially the left ventricle, from whence the blood 
is propelled into the arteries, and into all parts of the body. 

The right ventricle and auricle communicate with each 
other by an opening called the auriculo -ventricular orifice; 
to the two sides of which is attached an annular membrane, 
whose inner border is floating, and to which are fixed some 
tendinous cords. The latter are attached to some muscular 
bundles, or fleshy columns^ which arise from the inferior 
walls of the ventricle, and proceed towards the orifice: this 
membrane is called the tricuspid valve. Another one, 
analogous to this, and named mitral valve, exists at the 
orifice by which the left auricle and ventricle communicate 
with each other. It differs from the former by its greater 
solidity and more considerable resistance, which are capable 
of overcoming its tendinous filaments. The orifices of both 
the left and right ventricles, through which the blood 
escapes from the heart, are furnished with another kind of 
valve of a very diflferent construction to those already de- 
scribed. They are called semilunar valves, and are formed 



312 CIRCULATION OF BLOOD. LeCT. XVII. 

of three portions of membranes, which have, as their name 
indicates, a semi-circular form ; on one side they are 
adherent to the wall of the orifice, and on the other are free, 
so that when they are depressed, they present the form of 
three triangles, having for a common summit the centre of 
the vessel, and for a base, its circumference. They are 
pressed against the sides of the vessel, when a liquid column 
is driven out of the heart ; but, on the contrary, when a 
liquid attempts to pass back from the vessel to the heart, 
they immediately expand, and close the orifice. Thus then 
they allow the blood contained in the heart to escape by 
the vessels, and prevent the blood contained in the vessels 
from returning into the heart. 

Blood-vessels. — Lastly, we shall say a few w^ords respect- 
ing the blood-vessels. In the arteries, we remark a mid- 
dle membrane, very thick, and composed of circular fibres 
of a peculiar nature, called the yellow elastic tissue. To 
this the arteries owe their elasticity. The membrane^ 
composed of this tissue, is placed between the internal or 
serous membrane and the external membrane, composed 
of condensed cellular tissue. Three tissues likewise form 
the sides or walls of the veins ; but in these vessels the 
yellow elastic tissue is less obvious ; the internal membrane 
is enveloped by a thin layer of slight longitudinal fibres, of 
a loose texture ; and the external membrane is of a cellu- 
lar nature, and very resisting. The internal coat is thin^ 
smooth, resisting, and extensible. It forms in the cavities of 
some of the venous trunks numerous folds or valves,, which 
are so placed that they can diminish or even entirely ob- 
literate the diameter of the vessel, when a liquid column 
moves in a direction contrary to that of the course of the 
blood within them. 

The Circulation. — In a few w^ords we shall describe the, 
manner in which the circulation is eflfected. To give you 



Lect. XVII. 



THE CIRCULATION. 



313 



a correct notion of the way in which this function is per- 
formed, it is . sufficient to expose the heart of a rabbit or 



Fig. 23. 




The Anatomy of the Heart; 1, the right auricle; 2, the entrance of the superior 
vena cava; 3, the entrance of the inferior cava; 4, the opening of the coronary vein, 
half closed by the coronary valve; 5, the Eustachian valve ; 6, the fossa ovalis, sur- 
rounded by the annulis ovalis; 7, the tuberculum Loweri ; 8, the musculi peotinati 
in the appendix aiiricuJEe; 9, the auriculo-ventricular opening; 10, the cavity of the 
right ventricle; 11, the tricuspid valve, attached by the chordae tendines to the car- 
neae columnse; (12) 13, the pulmonary artery guarded at its commencement by three 
semilunar valves; 14, the right pulmonary artery, passing beneath the arch and be- 
hind the ascending aorta ; 15, the left pulmonary artery, crossing in front of the 
descending aorta ; *, the remains of the ductus arteriosus, acting as a ligament 
between the pulmonary artery and arch of- the aorta ; the arrows mark the course 
of the venous blood through the right side of the heart; entering the auricle by 
the superior and inferior cava, it passes through the auriculo-ventricular opening 
into the ventricle, and thence through the pulmonary artery to the lungs; 16, the 
left auricle ; 17, the openings of the four pulmonary veins ; 18, the auriculo-ventricu- 
lar opening ; 19, the left ventricle ; 20, the mitral valve, attached by its chordae ten- 
dineaB to two large coluuinag canieae, whicli project from the walls of the ventricle; 
•21, the commencement and course of the ascending aorta behind the pulmonary ar- 
tery, marked by an arrow; the entrance of the vessel is guarded by three semilu- 
nar valves ; 22, the arch of the aorta. The comparative thickness of the two ven' 
tricles is shown in the diagram. The course of the arterial blood through the left 
side of the heart is marked by arrows. The blood is brought from the lungs by the 
four pulmonary veins into the left auricle, and passes through the auriculo-ventri- 
cular opening into the left ventricle, whence it is conveyed by the aorta to every 
part of the body. 



314 CIRCULATION OF BLOOD. LeCT. XVII. 

Other mammal, and we shall then see the alternate con- 
traction and dilatation of the ventricles and auricles. When 
the right ventricle dilates, (he right auricle contracts, and 
vice versa: the same phenomenon takes place in the other 
side of the heart ; so that the movements of the homony- 
mous parts take place simultaneously, and are alternate 
with those of parts having a different name. At this mo- 
ment of the contraction of one of these cavities, the blood 
which it contains is expelled, and the direction which it 
takes is regulated by the arrangement and action of the 
valves placed at the orifice of this cavity. At the moment 
of the contraction of the right auricle the blood is forced 
towards the auriculo-ventricular orifice, and backward into 
the vence cavce. At this instant the ventricle dilates, the ori- 
fice opens, and very nearly the whole of the blood rushes 
into it ; a small quantity only regurgitating into the vense 
cavae. To these movements succeed the dilatation of the 
auricle, and the more energetic contraction of this ventricle. 
The blood which filled the ventricle is expelled from this 
cavity : two orifices present themselves, that of the pulmo- 
nary artery, and the auriculo-ventricular orifice. The lat- 
ter would allow it to return into the auricle, whose con- 
traction has just ceased, but for the action of the tricuspid 
valve, which opposes it, and whose structure is well 
adapted for this purpose. The blood, pressed on by the 
walls of the contracting ventricle, distends the membrane 
forming this valve, which yields until it becomes perpen- 
dicular to the axis of the ventricle, when the orifice becomes 
almost completely closed. But the fleshy columns, by con- 
tracting also, prevent the valve from turning over into the 
auricle, and retain it at the orifice. On the same princi- 
ple, valves in all our hydraulic machines are constructed. 
The semi-lunar valves, placed at the orifice of the pulmo- 
nary artery, on the contrary, yield to the impulse of the 



LeCT. XVII. THE CIRCULATION. 3l5' 

blood, and leave this orifice free ; hence the blood escapes 
into the artery in consequence of the construction of the 
valves, which open from within outwards. 

The arrangement of the valves, in the left cavities of 
the heart, is similar to that in the right cavities just no- 
ticed. When the left auricle dilates, the blood from the 
pulmonary vein enters it ; and at the moment when it con- 
tracts, which circumstance coincides with that of the 
dilatation of the ventricle, the blood is propelled into the 
latter, and from this into the aorta, in consequence of the 
contraction of the ventricle. 

Two successive sounds reach the ear when applied to 
the chest, corresponding to the two successive movements 
of the heart ; the auricles dilate together : and the ventri- 
cles likewise. 

By contraction of the heart we mean that of the ven- 
tricles: their contraction is called systole^ their dilatation 
dyastole. 

We have thus sketched the principal features of the me- 
chanism of the circulation. As for the details, they are 
not within the limits of the present course, and, there- 
fore, it is not our province to explain them to you. I 
"would have even suppressed what little I have said on 
this subject, had I not considered it absolutely necessary 
to precede the study of the phenomena of the circulation 
of the blood by an exposition of these elementary anato- 
mical facts. 

The Blood. — The liquid which circulates in the vessels 
is of a vermilion red colour, in the arteries, and of a dark 
red in the veins. It is slightly alkaline, has a specific 
weight of 1-0527 to 1-057, and holds in suspension glo- 
bules of a greater or less diameter. In most mammals 
these globules are circular discs ; while in birds, reptiles, 
and fishes, they are elliptical. This liquid constitutes the 



316 CIRCULATION OF BLOOD. LeCT. XVII. 

blood. The quantity of it varies in different animals, and 
there appears to exist a certain ratio between its weight 
and that of the animal. Valentin has pointed out an inge- 
nious method of determining its total quantity : it consists in 
first ascertaining the percentage quantities of water and-solid 
matters contained in the blood drawn from an animal by 



Fig. 24. 







Red Corpuscles of Human Blood, represented , at a, as they are seen when rather 
beyond the focus of the microscope ; and at b as they appear when within the focus. 
Magnified 400 diameters. 

a small bleeding. A given weight of water is then to be 
injected into one of these blood-vessels, and again we must 
ascertain the percentage composition of the blood thus 
diluted, that is, the proportion between the water and solid 
constituents. It is easy to perceive how, with these data, 
we may obtain the amount of the total quantity of the blood. 

It is assumed that man contains, on an average, from 
12 to 15 kilogrammes [about 30^^ to 40i troy pounds] of 
blood. The ratio which exists between the weight of the 
blood and that of the man will be about 1 to 5. 

JYumber of Pulsations.— The heart of an adult man con- 
tracts from seventy to seventy-five times in a minute ; but 
the number of pulsations varies according to the age, sex, 
temperament, and idiosyncrasies of individuals, the species 
of animal, and the pressure of the atmosphere. Thus in 
the new-born infant the number of pulsations is from a 
hundred and thirty to a hundred and forty ; in fishes, from 



LeCT. XVII. CIRCULATION OF BLOOD. 317 

twenty to twenty-four ; in the frog, sixty ; in birds, from 
a hundred to a hundred and forty. Parrot ascertained 
that his own pulse was a hundred and ten, at an elevation 
of 4000 metres [= 13123 English feet] above the level of 
the sea, while the number at the level of the sea, was only 
seventy. 

Velocity of the Circulation. — Let us now speak of the 
velocity of the movement of the blood. The researches 
made on this subject may be divided into two classes i first, 
it is important to determine how much time the blood oc- 
cupies in traversing the whole system ;, afterwards we must 
examine the velocity with which the blood traverses cer- 
tain parts of this circle ; in short, with what speed it moves 
in the arteries, the capillaries, and the veins. 

We are indebted to Hering for some of the experiments 
on the first class of these investigations. A solution of fer- 
rocyanide of potassium was injected into the Jugular veins of 
a horse, and at the same instant the blood which escaped from 
the opposite jugular was collected. It was received in num- 
bered vessels, which were changed successively at equal in- 
intervals, by counting with a chronometer the number of 
seconds which elapsed from the commencement of the ex- 
periment to the moment when the blood was collected in the 
last vessel. 

In an experiment which I had occasion to make with 
Professor Piria, and which was performed on a horse, the 
blood of one jugular was collected at the moment when the 
ferrocyanide was injected into the other, and the receiver 
was changed every five seconds.- We found that the blood 
which escaped twenty or twenty -five seconds after the in- 
jection, contained traces of the ferrocyanide. These num- 
bers agree with those of Poiseuille and of Hering. 

Poiseuille, when repeating these experiments, first ascer- 
tained that, notwithstanding the isitroduction of the ferrcr 



318 NUMBER OF PULSATIONS. LeCT. XVII. 

cyanide, neither the number of pulsations, nor the force of 
the heart's contractions varied. But, like Hering, he dis- 
covered traces of the ferrocyanide in from tw^enty or twenty- 
five seconds after its introduction. 

I cannot refrain from relating some of Poiseuille's experi- 
ments, made for the purpose of ascertaining the influence 
which certain substances mixed with the blood had on the 
velocity of its circulation. He found in every case, that 
the number of pulsations, and the force of the contractions^ 
were unaltered. When a solution of acetate of ammonia 
was injected along with the ferrocyanide the latter was de- 
tected in about eighteen seconds; and nitrate of potash 
gave an analogous result, but extending this interval to 
twenty seconds. On the contrary, when a little alcohol was 
added to the ferrocyanide injected into the jugulars, the 
latter did not escape from the opposite vessel until after 
forty or forty-five seconds. The influence of these sub- 
stances upon the rapidity of the circulation merits especial 
attention, for it is connected with a fact entirely within the 
domain of molecular physics. Poiseuille ascertained, in an 
important investigation on the passage of water, serum, &c., 
in capillary tubes, that these substances acted there abso- 
lutely in the same way as in the sanguineous circulation. 
It is not, however, to be supposed that it is by this kind of 
influence that many other substances introduced into the 
blood, act; for a great number of them exercise their in- 
fluence upon the nervous force, and through this on the 
contraction of the muscular fibre of the heart. Thus, a 
small quantity of an infusion of coflfee injected into the 
veins of a dog, instantly augments the force of the heart's 
contraction, while a solution of opium diminishes its energy. 

The rapidity of the circulation, that is, the time which 
•a molecule of blood occupies in passing from the right to 
the left ventricle, seems, at first sight, to have been very 



LeCT. XVII. VELOCITY OF THE CIRCULATION. 319 

accurately ascertained by the before-mentioned experiments 
of Hering, and the numbers given by him are very gene- 
rally adopted. But it appears to me easy to show that his 
method is liable to several errors, and that his results are 
far from expressing the duration of the circulation. If, in 
place of introducing into the vein a liquid solution, the 
presence of which we must afterwards detect in the opposite 
vessel, we could cause a small body, of a density equal to 
that of the blood, to pass there, and which would accom- 
pany the blood when traversing the capillaries and the whole 
circulatory system, the period which elapsed, from the 
moment of its introduction into one jugular to its appear- 
ance in the other, would be precisely the time required. 
But we must bear in mind that, if a solution susceptible of 
mixing with another be poured into any part of the latter, 
we soon find it in the entire mass, even supposing that it be 
much more considerable than that of the first, and without 
any motion. Two solutions, capable of mixing, diffuse 
themselves, and rapidly mix in consequence of the effects 
of chemical action, aided by the physical properties of the 
liquids. Hence, it is not necessary, for the kind of diffusion 
oi which we are now^ speaking, that the ferrocyanide should 
have traversed the entire circulatory circle. It must be 
especially observed, that it is impossible to introduce a 
liquid solution into the veins without propelling it by a 
pump, and employing a force which, it is obvious, is con- 
siderable, since it must overcome the pressure exercised by 
ihe blood, so that the mixture of this solution with the san- 
guineous mass is promoted, more or less, according to the 
degree of force employed. 

In consequence of these objections, I cannot admit the 
accuracy of the nurnbers given to show the time in which 
the blood accomplishes its entire circulation; and this 



^3.20 CIRCULATION OF BLOOD. LecT. XVII. 

method appears to me to be incapable of furnishing correct 
results. 

Moreover, there exists another mode of experimenting, 
which the celebrated Hales first applied to the investigation 
of the velocity of the circulation. It is based on a princi- 
ple essentially accurate, and consists in deducing the velocity 
from the capacity of the ventricles, and from the number of 
pulsations of the heart in a given time. 

Hales measured the rapacity of the left ventricle of a 
horse, and of several other animals, by taking a cast of the 
ventricle, by pouring melted wax into it, and allowing it 
to solidify therein. He found, that the capacity of the left 
ventricle of a mare was equal to 10 cubic inches; and the 
weight of 1 cubic inch of blood being 267*7 grains, it follows 
that the total weight of the blood contained in the ventri- 
cle was about 6 ounces avoirdupoise. Assuming that, at 
each pulsation, the ventricle completely empties itself, 6 
ounces of blood would be expelled at each contraction, 
and seventy-two of these contractions would be necessary 
^0 efTect the complete circulation of the 36 pounds (troy) 
of blood which the horse contains. His result is very dif- 
ferent from that obtained in the experiments of Hering, 
relative to the velocity of the circulation. For, if the heart 
of a horse made only sixteen pulsations in twenty-five 
seconds, there could not escape from the ventricle, in that 
interval of time, more than 8 pounds (troy) of blood. It 
would be difficult to account for such a very great discre- 
pancy in these results, if we assumed Hering's numbers to 
be correct. 

We shall here quote the numbers given by Hales for the 
time required for the completion of the circulation in man. 

Assuming seventy-five pulsations per minute, from 24 to 
30 pounds for the weight of the total mass of blood, and 2 
ounces to be about the quantity thrown out at each con- 



LeCT. XVII. VELOCITY OF THE CIRCULATION. 321 

traction of the left ventricle, a hundred and ninety-two pul- 
sations would be necessary to make the entire mass circu- 
late ; that is, about two minutes and a half. 

It is, however, but right to observe, that we cannot 
assume that all the blood of the ventricle would be expelled 
at each pulsation ; consequently, the numbers given must 
always be below the true ones. 

It remains now for us to speak of the velocity of the 
blood in the different vessels of the circulatory system. 
Assuming the section of the orifice of the left ventricle to 
be equal to that of the aorta, and that the sum of the sec- 
tions of the different branches into which it divides, is also 
the same, it follows that if the same quantity of blood pass 
every where in the same interval of time, the velocity will 
be the same in every vessel. But the sections of the 
arterial and venous trunks are not really equal to those of 
their ramifications. The most simple observation proves, 
on the contrary, that the sum of the sections of the small 
vessels is more considerable than that of the trunks. Look 
at the heart of an ox, in which we have divided the arte- 
rial and venous trunks, the orifice of the aorta is about 28 
millimetres, while that of one of its trunks is about 20, and 
the other 16 : the venae cavse have a total diameter of 76 
millimetres. The well-known law of Castelli ought to be 
applied, in order to obtain the velocity of the blood at dif- 
ferent parts of its course : this velocity will always be in 
the inverse ratio of the sections. If we could accurately 
estimate the ratios which exist between the sections of the 
various vessels in which the blood circulates, it would be 
easy to determine what would be the velocity in all the 
vessels ; the quantity of blood thrown out of the left ven- 
tricle being known, as well as the time employed in expell- 
ing it. 

I shall content myself with showing you by one illustra- 
21 



322 CIRCULATION OF BLOOD. LeCT. XVII. 

tion, how we may determine the velocity with which the 
blood circulates in the aorta : I adopt the numbers given by 
Hales. The quantity of blood expelled from the left ven- 
tricle of the heart of a horse, is about 10 cubic inches; the 
area of the aorta is 1-036 square inches ; the fraction y;^^"-^ = 
9-64 expresses the length of the cylinder of blood which is 
formed in passing through the orifice of the aorta at each 
systole of the ventricle ; and, as the heart of the horse 
makes thirty-six pulsations per minute, that is, 2160 per 
hour, it follows that a column of blood [2160 X 9-54 inches 
or] 1735 feet long will be thrown into a vessel of the calibre 
of the aorta every hour. Then, estimating the systole to 
continue only one-third of the interval between the pulsa- 
tions, the velocity will be found to be thrice as much, 
namely, 86 feet per minute. 

Hales, who studied the phenomena of the circulation 
with so much sagacity and skill, endeavoured to determine 
experimentally the velocity of the blood in the capillary 
vessels. For this purpose, he introduced warm water into 
the descending aorta of a dog, by means of a tube thrust 
into the artery. The pressure exercised by the column of 
liquid, was nearly equal to that which the blood experiences 
in this vessel [from the contraction of the heart.] The 
intestines having been slit open from end to end, the water 
was seen to ooze out, drop by drop, from the capillaries. 
Hales varied the experiment, by successively dividing the 
vessels nearer and nearer to the aorta; and, at the same 
time, measured the water which passed oflf, in a given time, 
by the various capillaries, whose diameter he knew. The 
pressure of the column of liquid was kept constantly equal. 
Here are some of the numbers obtained : 342 cubic inches 
escaped from the capillary vessels in 400 seconds ; the same 
quantity passed off by the mesenteric arteries 140 seconds; 
and by the crural arteries in 20 seconds. 



LeCT. XVII. VELOCITY OF THE CIRCULATION. 323 

Although the numbers may be far from expressing the 
absolute velocity of the circulation in different vessels, they 
are, nevertheless, sufficient to prove that the velocity dimi- 
nishes in proportion to the distance from the heart, and to 
the smallness of the sections of the vessels. Notwithstand- 
ing the remarkable augmentation in the sum of the sections 
of the branches, in comparison with those of the trunks, it 
is certain that the velocity of the circulation is diminished, 
and becomes much less than that which it would have been 
if the partial sections had been united and formed into a 
single vessel. This diminution of velocity is occasioned 
by the friction of the fluid against the sides of the vessels, 
by the large folds, the numerous curves, and the resistance 
of the liquid column put in motion. On account of the 
great number of anastomoses, between the ultimate arterial 
trunks and the extremities of the arterial and venous capil- 
laries, and which are especially remarkable in the lungs, 
the velocity of the blood suffers less diminution than it 
would otherwise do. In this way the lengths of the small 
tubes are diminished as much as possible, and precisely in 
proportion as the sum of the sections of the ramifications 
exceeds the sections of the trunk from which they arise. 

A beautiful object of experimental physiology, is the 
microscopic examination of the capillary circulation of the 
lungs of the salamander, or that of the mesentery and the 
claw of the frog. We perceive the globules of blood 
moving with more or less rapidity within small vessels, w^ith 
a velocity which varies according as the section of the 
vessels is greater or less. 

Pressure on the J^lood. — I must now speak of the pres- 
sure which the blood sustains in the vessels in which it 
circulates. The investigation of this subject has engaged 
the attention of physiologists of all times, and they have 
pursued different ways in their experiments. Such, also, 



324 



CIRCULATION OF BLOOD. 



Lect. XVII. 



Fig. 2; 



has been the case with respect to the investigation of the 
force with which the left ventricle contracts. Borelli, 

Bernoiailli, and Keil, obtained 
numbers which differ very con- 
siderably from each other. 
Thus, BorelU estimates the 
force of the heart as equivalent 
to that of 180,000 pounds; 
w^hile Keil, on the contrary, 
calculates it at only 5 ounces. 

Kales was also the first who 
made accurate experiments for 
measuring the pressure of the 
blood in the arteries; but it is 
to Poiseuille that we are in- 
debted for the most complete 
kivestigation of this subject. I 
shall confine myself to an ex- 
position of his principal conclu- 
sions. 

The haemo-dynamometer of 
Poiseuille consists of a kind of 
glass manometer, w^hose short, 

HrBmo-dynamometer of Poiseuille. i^Q^J^Ontal arm is placed in a 
A bent glass tube, nlled with mercury _ ' 

in the lower part, a <^ e. The horizon- braSS tubc, which is aftcrwards 

tai part b, is provided with a brass ini^oduced into the artcrv of the 

head, which hts into the artery. A _ •/ 

small quantity of a solution of the living animal. In Order to pre- 

carbonate of soda is interposed be. ^.^^^^ ^^^ COagulation of the 

iween the mercury and the blood, to "^ 

prevent its coagulation. When the blood, which obstrUCtS the por- 

bl.od presses on the fluid in the hori- ^|^^ ^f ^j^^ ^^^^ situatcd bctWCCn 

zontal limb, the rise of the mercury 

lowardse, measured from the level to the artery and the Column of 

which it has fallen towards a gives ^^^.^^ Poiseuille firSt fills 

the pressure under which the blood . 

moves, this with a solution of carbonate 

of soda. We then see the column of mercury in the long 
Y^rtLcal; arm risej^ and i:em.aia, at a hjeight which Gontinu-es. 




LeCT. XVII. PRESSURE ON THE BLOOD. 325 

constant throughout the experiment. The difference in the 
level of the two columns of mercury, indicates the pressure 
exercised by the blood against the corresponding section of 
the wall of the vessel into which the tube of the apparatus 
is introduced. Poiseuille made a great number of experi- 
ments upon the arteries of different animals, and upon 
various arteries of the same animal ; and the most important 
fact which he demonstrated is, that the pressure of the blood 
in the arteries is the same, whatever be the part of the 
arterial system, the diameter of the vessel, its distance from 
the heart, and the position of the branch experimented on, 
in relation to the trunk from which it is derived. Thus, 
Poiseuille found that the pressure obtained, by applying the 
hsemo-dynamometer to the carotid artery of a dog, at a dis- 
tance of 180 millimetres from the heart, is the same as that 
of the aorta at 370 millimetres : the diameter of the aorta 
being 9 millimetres, and that of the carotid 4 millimetres. 
In both cases the pressure was measured by a column of 
mercury 84 millimetres in height. This experiment, made 
on a horse, gave the same result, when performed on two 
arteries, the diameter of one of which w^as five times greater 
than that of the other: the pressure made by both was equal 
to that of a column of mercury of 146 millimetres. It is 
curious to observe, that the pressure, in different animals, 
has no relation to their weight. 

This result, which it is right to have had demonstrated 
by experiment, ought not, however, to astonish us when w^e 
reflect that it is a necessary consequence of the principle of 
the equality of pressure of liquids. The impulse given by 
the column of blood expelled from the left ventricle, to that 
contained in the aorta, is immediately propagated equally 
to the whole mass of blood, filling both the large and small 
arteries. 

It is this impulse, which takes place at the moment w^hen 
the ventricle propels the blood into an artery and into al] 



326 CIRCULATION OF BLOOD. LeCT. XVII. 

its branches, that produces the well-known phenomenon of 
the pulse, and which we know to be isochronous with the 
contraction of the ventricle. 

Adopting the numbers given by the experiments of 
Poiseuille, we have then the pressure supported by the 
walls of the heart and of the arteries. This pressure is 
always equal to the weight of a column of mercury, which 
has for its base the area of the artery or the superficies of 
the ventricle, and for its height, that obtained by means of 
the hsemo-dynamometer. From these data, Poiseuille cal- 
culated that at the moment of the contraction of the heart 
the blood is propelled into the aorta of a man, twenty-nine 
years of age,* exercised against the column of liquid which 
fills it, supposing this to be at rest — a pressure equal to 
1-971779 kilogrammes [= about 5J lbs. troy.] In the 
radial artery this pressure is no more than 15*35 grammes 
[about 137 grains troy.] By knowing exactly the internal 
surface of the left ventricle, at the moment of contraction, 
we can easily calculate the pressure exercised upon these 
walls at this moment. 

Among the most important results of Poiseuille's experi- 
ments, I would also mention that which shows the constancy 
of the variations in the height of the column of mercury in 
the hsemo-dynamometer, during the respiratory movements- 
This height is invariably greater during expiration, than 
during inspiration; and this difference is observed in large 
as well as in small arteries; though it is more or less con- 
siderable in different animals. 

It is proper, also, that I should draw your attention to 
the fact, that the height of the column of the haemo-dyna- 
mometer likewise varies according to the position of the 

* It is assumed that the column of mercury raised in the haemo-dyna- 
momeler, applied to man, should be 160 millimetres, and the diameter of 
the aorta 34 millimetres. — Note by Maiteuccu 



LeCT. XVII. PRESSURE ON THE BLOOD. 327 

animal. I have always remarked, that when this instru- 
ment is introduced into the carotid, the column of mercury 
rises several millimetres when we raise the animal by its 
hind part, and falls when we place it in an opposite posi- 
tion. The cause of this difference is evident. We must, 
therefore, presume, that in all Poiseuille's experiments, in 
which he compared the pressure of the blood in different 
vessels, the animal was kept in the same position. 

I cannot pass over in silence the dilatation of arteries at 
every pulsation. We are indebted to Poiseuille for proving 
beyond doubt the existence of this phenomenon, which has 
so great an influence upon the circulation. He laid bare a 
certain portion of the carotid artery of a living horse, and 
enclosed it in a metallic tube filled with water. This tube 
had an opening closed by cork, in the centre of which was 
fixed a small glass tube. At every contraction of the left 
ventricle the liquid rose in the tube, and fell again when the 
contraction ceased. Thus, then, after the dilatation of the 
artery, occasioned by the impulse of the blood, the arterial 
coats return to their former state in virtue of their elasticity. 
Poiseuille endeavoured to measure this elastic force dis- 
played by the arterial coats ; and without adopting his con- 
clusion, that the force of contraction of the coat exceeds that 
of the dilating force, it is certain that, when the contraction 
of the ventricle, the principal force which puts the blood in 
motion, ceases, the elasticity of the arterial coats, which 
recover themselves, also propels the blood, and thus adds 
to the force of the heart. 

Lastly, I must say a few words respecting the researches 
which this physiologist, already so frequently quoted, has 
made on the movement of the blood in the capillaries. 
Poiseuille observed, in a great number of experiments, that 
the motion of the blood in the vessels ceases when the heart 
is raised or bound, and that this movement continued only 



328 CIRCULATION OF BLOOD. LeCT. XVII. 

for a few minutes, on account of the diminution of volume, 
and of the kind of contraction which the elastic coats of the 
vessels suffer when the blood ceases to be propelled by the 
heart. By the aid of the microscope there was seen an im- 
moveable layer of serum, adherent to the coats of the ves- 
sel ; and the liquid blood thus moves in this tube, formed 
by its own substance. Poiseuille examined the passage of 
the same liquid, both in a glass capillary tube, and in a ca- 
pillary blood-vessel of a living or dead animal, and found 
that it followed the same laws in all cases. This fact as- 
suredly proves, that in these various cases the liquid really 
circulates in a tube always formed of the same matter; that 
is to say, of an immoveable and adherent liquid layer, and 
which is the same as the liquid which flows through, what- 
ever may be the material of the tube. Lt is curious to ob- 
serve that the capillary circulation continues uninfluenced 
either by a vacuum or by a pressure of eight or ten atmo- 
spheres. 

Having explained to you, as far as the limits of this course 
will permit me, the most accurate and conclusive experiments 
upon the various questions relating to the sanguineous cir- 
culation, we have now all the necessary elements for giving 
an account of the mechanism of this function. 

I consider it useless to detain you longer for the purpose 
of experimentally demonstrating, that the contraction of the 
heart and the elasticity of the coats of the vessels, especially 
of the arteries, are the principal powers of the circulation. 
If we tie an artery in a living animal, the vessel almost en- 
tirely empties itself of blood, and the circulation continues 
in it only for a short space of time. The contrary happens 
with the ligature of a vein ; for in that case the blood soon 
accumulates, and the vein swells below the ligature. I 
shall confine myself to the relation of a single experiment 
by Magendie, The crural artery and vein of a dog were 



LeCT. XVII. PRESSURE ON THE BLOOD. 329 

laid bare, and a ligature applied to the vein : an incision 
was then made below the ligature, and a jet of blood 
escaped. When the artery was pressed between the fin- 
gers, in order to prevent the passage of the blood within it, 
the jet of venous blood diminished, and was ultimately 
stopped completely ; but when the pressure was removed, 
the jet re-appeared. These phenomena could be repro- 
duced several times. The conclusion drawn from this fact 
is evident : the blood traverses the capillaries, and circu- 
lates in the veins by the sole forces which have propelled 
it into the arteries, namely, by the contraction of the left 
ventricle, and that of the arterial coats, which are the chief 
powers, the only ones, in fact, of the circulation. 

The influence which atmospheric pressure exercises upon 
this function is very limited. I have already mentioned, 
that at each experiment the column of mercury, of the 
haemo-dynamometer, applied to the artery, rises; and at 
each inspiration it falls. Poiseuille observed the same 
phenomenon, and under the same circumstances, in large 
venous trunks : thus, in the jugulars the column of mercury 
rises during expiration and falls during inspiration. These 
phenomena do not occur vv-hen we make the experi- 
ment upon venous trunks distant from the thoracic ca- 
vity. We easily understand that when the latter dilates, 
the pressure of the atmosphere must compress the veins, 
and thus, by means of valves, so placed in these ves- 
sels as to impede the return of this liquid, it assists in 
making the blood move towards the heart. On the con- 
trary, during expiration, when the thoracic cavity is con- 
tracted, all the vessels contained within it are simulta- 
neously compressed. Experiment has shown, that the va- 
riations of the pressure of the blood in the arteries and the 
veins, correspond to the respiratory movements, and cease 
to manifest themselves in the sanguineous trunks situated 
beyond this cavity. 



»330 CIRCULATION OF BLOOD. LeCT. XVII. 

The muscular contraction of the heart, and the contrac- 
tion of the arterial coats, are then the principal motive 
powers of the sanguineous circulation. The combination 
of these two forces in the mechanism of this function is so 
perfect, that the movement of an intermitting jet, produced 
by the alternate contractions of the heart, is transformed 
into a continued movement by the elastic force with which 
the arterial coats are endowed. By this force the arteries, 
which were at first dilated, recover themselves, and conse- 
quently propel the blood forward, at the moment when the 
contraction, which has thrown the blood into the arteries 
and caused them to dilate, ceases. 

Let us imagine, then, a circu arsystem of tubes of diffe- 
rent diameters, and having elastic sides ; and that the tw^o 
extremities or apertures of this system open into two cavi- 
ties separated from each other, and of which the walls can 
approximate and separate like those of a pair of bellows. 
When we fill this tube with a liquid, and rapidly close one 
of these cavities by depressing its moveable wall, the liquid 
which it contains is urged into the tube, and thus pushes 
onward the liquid column. This advances by a movement 
which soon becomes uniform, and is rapidly communicated 
to the entire mass. In the mean time, the other part of the 
bellows opens ; the liquid which filled the tube in the op- 
posite extreme, advances also, and is easily projected into 
the dilated cavity. If the walls of the tube were not elastic, 
the movements would be intermittent, and would cease as 
soon as the bellows could no longer open; but they become 
continuous, because the walls are endowed with that pro- 
perty which begins to be exercised precisely at the moment 
when the bellows shuts, and the action lasts during the 
whole time that they remain at rest. The function which 
I have described, by supposing it to take place with a pair 
of bellows, is that which is performed by the heart. The 



LeCT. XVII. PULMONARY CIRCULATION. 331 

walls of the left ventricle thus approach each other, con- 
tract with a great rapidity, which can be determined when 
we know the exact duration of the contraction and the 
quantity of blood expelled. The capacity of the ventricle 
is thus diminished, and a certain quantity of blood thrown 
into the aorta, and a movement communicated to it which 
is propagated throughout the system. At the instant that 
the arteries dilate, the right ventricle opens, and the blood 
enters it. The contraction of the left ventricle ceasing, the 
arteries return to their original condition, and again propel 
the bloo d forward. 

Pulmonary Circulation. — We have passed over in silence 
all that which relates to the pulmonary circulation, this 
being produced by the same causes, and under the same 
laws as the circulation in the rest of the body. 

Conclusion. — Thus, then, by the arrangement of the 
various parts of the sanguineous system, is solved, by a 
very simple mechanism, and conformably to the physical 
laws of the movements of fluids, a very complicated hy- 
draulic problem : namely, that of the continued distribution 
of the same liquid in a system of tubes, having different 
diameters in different parts of the body, and, consequently, 
with very variable velocities, and always in relation to the 
functions of these parts, and all this by the simple alternating 
impulsion given to this fluid by the sudden contraction of a 
species of sac, which makes a part of the tube itself. 



332 VOCAL APPARATUS. LeCT. XVIII. 



LECTURE XVIII. 

VOCAL APPARATUS. THE VOICE. 

Argument. — Description of the human vocal organ. Experiments demon- 
strative of the seat and mechanism of the voice : structure of the vocal 
cords. Analogies between the human voice and musical instruments. 
Description of reed-instruments. The human vocal organ is a reed-in- 
strument vi'ith membranous lips. Results of Miiller's experiments on 
the larynx. Qualities of the human voice. The human vocal organ is 
infinitely superior to any musical instrument. Artificial caoutchouc, 
larynx. 

After the lectures on the nervous force and muscular 
contraction, I must immediately proceed to the considera- 
tion of the production of sound in animals; which here, as 
in all other cases, is caused by a vibratory movement. In 
the vocal organ this movement is produced by the contrac- 
tion of muscles, and of parts subjected to their influence, 
and from them, therefore, the voice takes its origin. 

Organ of Voice in Man. — In order that I may be enabled 
to explain at sufficient length, the theory of the vocal organ 
of man and animals, I must not pass over in silence the de- 
scription of its constituent parts. It is easy to prove, ex- 
perimentally, the position occupied by this apparatus. A 
very superficial examination shows us that the voice is pro- 
duced when air is expelled from the lungs ; and every one 
knows that it is impossible to articulate sounds when we 
close the mouth and nose. It is, therefore, evident, that 
the vocal organ resides in a certain portion of the tube which 



LeCT. XVIII. ORGAN OF VOICE IN MAN. 



333 



FiiT. 26. 



Fi(r.2 




A FiioNT View of Ligaments of L.i^jynx. 



1. Dddy of the Os Hyojdetf. 

2 Its Anpejidices. 

?,. Its Cornna. 
4.5. Tnvreo-Hvoirt Lisampnt. 

(•. Lateral Thyreo-Hyniil Lisrament. 

7. Cornu Majus of each Half uf the Thy- 
roid Cartilage. 

F. Si.les of thf Thyroid Cartilage. 

9. Us Projpcling Angle. 
30.11. Crico-Thyroid Ligament. 

12. Cornu Minus of each Side of the Thy- 
roid Cartilage. 

13. First Ring of the Trachea. 

Fiir. 28.. 




A Latehal View of the; same. 

1. Os Hvdiiles. 

2L. Thyrcn-IIyoid LiaaniPnt. 

3. Cornu Majus of the Thyroid Carti- 
lage. 

4. Its An^le and Side. 

5. Cornu Minus. 

6. Lateral Purtion of the Cricoid Carti- 
lage 

7. Rings of the Trachea. 




A Vertical Section of the Larynx to 
SHOW ITS Internal Surface. 

1. Section of the Root of the Tongue. 

2. Os Hyoidps 

3 The Muciparous Gland of the Epiglottis. 

4. Tup of the Epielottis Cartilage. 

5. A Section of its .Anterior Face. 

6. A Fuld of Mucous Membrane from the 
Arytenoids to the Epiglottis. 

7. Superior Vocal Ligament. 

8. Section of Thyroid Cartilage. 

9. Ventricle of Galen or Morgagni. 
JO. Lower Vocal Ligament. 

11. Arytenoid Cartilages. 

12. [nside of the Cricoid Cartilage. 
1.3. Its Posterior Portinn. 

14 T ining Memhranps of the Trachea. 

15. End of the Cornu Majus of the Os Hyoides. 

IG. Cornu Majus of the Thyroid Cartilage. 

17. Mucous Membrane of tlie Pharynx. 

18. CEsophagiis. 

19. Tlij?r.oid GJand. 



SM vocal apparatus. Lect. XVIII. 

proceeds from the bronchi and terminates in the mouth. 
To determine more accurately its position, we have only to 
observe that if an opening be accidentally or purposely 
made in the trachea of a man, below the larynx^ it is im- 
possible to produce a sound ; but, if we close the opening, 
the power of producing the voice immediately returns. If, 
however, the opening be made above the larynx, the voice 
remains as before. In birds the organ of voice is situated 
at the bifurcation of the trachea ; that is to say, it occupies 
a lower situation in them than in mammals ; and, hence, 
after cutting off" the head of a bird, we may still succeed in 
obtaining sounds by the compression of the thorax. 

We shall describe the vocal organ of man as being the 
most complicated and the most perfect. The trachea is a 
species of tube formed of cartilaginous rings, separated from 
each other by membranous and flexible rings. The lower 
end of this pipe divides into two branches, which subse- 
quently ramify in the parenchyma of the lungs, somewhat 
like the branches of a tree. The upper part of the pipe 
opens in the buccal cavity, and is terminated by the larynx, 
the true organ of voice. We may regard the larynx as a 
continuation of the trachea, but with this difference, that 
the portion of the tube, composing it, is broader, and is 
attached to the os hyoides. It consists of four cartilages ; 
namely, the cricoid^ the thyroid^ and the two arytenoid. 
They are of very different shapes, are articulated one to the 
other, and are united to the upper ring of the trachea. 
Several muscles are attached to the larynx, and by their 
contraction the entire larynx, or some of the cartilages 
composing it, are moved. The mucous membrane lining 
the larynx, forms, at about the middle of this organ, two 
large lateral folds directed transversely, and which have the 
appearance of a button hole : these folds are called the vocal 
cords, or the inferior ligaments of the glottis. Above them 



LeCT. XVIII. ORGAN OF VOICE IN MAN. 



335 



we find two other folds, analogous to the preceding, and 
which are termed the superior ligaments of the glottis. The 
cavities formed by this arrangement, between the superior 



Bird's eye view of the larynx 
from above, g e h, the thyroid 
cartilage, embracing the ring of 
the cricoid r u x w, and turning 
upon the axis x z, which passes 
through the lower horns, n f, 
N F, the arytenoid cartilages, 
connected by the arytenoideus 
transversus; t v, t v, the vocal 
ligaments; n x, the right crico- 
arytenoideus lateralis (the left 
being removed ;)v kf, the left thy- 
ro-arytenoideus (the right being 
removed ;) n ^, n I, the crico-aryte- 
noidei postici ; b, b, the crico- 
arytenoid ligaments. 



Fig. 29. 




and inferior ligaments, have received the name of ventricles 
of the larynx. The chink directed from before backwards, 
and comprised between the two vocal cords, is called the 
glottis. Lastly, above this chink, we observe a fibro-carti- 
laginous tongue-like body, fixed by its base beneath the" 
root of the tongue ; and which in the act of deglutition is 
inclined downwards, so as to cover the glottis, but during 
expiration is placed obliquely: this body is the epiglottis. 
The dimensions of the glottis are as follows: its length is 
from 25 to 30 millimetres; the space between the two lips, 
which is extremely small in front, is from 7 to 8 millimetres 
posteriorly: these lips, moreover, are capable of being 
brought nearer together, so as to touch. The depth of the 
ventricle is from 25 to 30 millimetres, and their greatest 
possible height 15 millimetres. The superior walls of the 



B36 VOCAL APPARATUS. LecT. XVIII. 

ventricles are so close together that they form a kind of 
second glottis, at from 15 to 18 millimetres above the 
other one. 

Seat of the. Voice. — The air expelled from the lungs with- 
out any extraordinary effort easily traverses the larynx 
without producing sound. From the time of Galen, an 
experiment has been known which shows, that to articulate 
a sound, it is absolutely necessary to contract the muscles 
of the larynx. This experiinent consists in wounding the 
laryngeal nerves, or in effecting their complete division on 
both sides of the trachea: in this case, paralysis of the 
larynx is complete, and the power of forming sounds is 
entirely destroyed. By another experiment, we can ascer- 
tain still more exactly the part of the organ which is the 
most essential for the production of the voice. If we re- 
move the superior ligaments of the glottis, the voice con- 
tinues, though it becomes more feeble ; but if we divide 
or injure the inferior ligaments, namely, the vocal cords, 
the voice is completely destroyed. Miiller ascertained that 
it is easy to obtain sounds from the larynx of the dead human 
subject,' by forcing air through the trachea ; provided that 
the inferior ligaments of the glottis be rendered in some de- 
gree tense, and the aperture of the glottis narrowed. Ac- 
cording to this learned physiologist, the experiment likewise 
succeeds when all the parts above the glottis, such as the 
epiglottis, the superior ligaments, and the ventricles of the 
larynx, are removed. If the vocal cords alone remain, and 
the chink between them be narrow, sound is always pro- 
duced. Magendie laid bare the glottis in living animals, and 
saw that the vocal cords were thrown into vibration, when 
cries were uttered. I propose to show you one of Longet's 
experiments, to prove the part which the vocal cords take 
in the production of the voice. I have here a rabbit, whose 
larynx bas beea laid bare ; and you observe that the animal 



LeCT. XVIII. VOCAL CORDS. 337 

cries whenever we pinch any part of its body. You per- 
ceive that, at the same time, the crico-thyroid muscles con- 
tract. By the contraction of these muscles the vocal cords 
are rendered tense, and brought nearer together. After 
having divided the nerves going to these muscles, their 
contraction can no longer be effected ; and if we then pinch 
the animal it no longer cries, and we can hear only some 
very grave and hoarse sounds. We may, therefore, con- 
clude that the glottis constitutes the organ of the voice; 
that the trachea may be compared to the bellows' pipe of 
an organ ; and that the upper part of the larynx, and all 
the parts situated above the epiglottis, including the cavities 
of the mouth and nose, form the upper tube of this instru- 
ment, which serves merely to modify the sound, as may be 
easily shown by effecting some alteration in this cavity. 

Vocal Cords. — The vocal cords are formed of that elas- 
tic tissue, which is remarkable for its yellow colour, for the 
arrangement of its fibres, and for forming the middle coat 
of the arteries, and a great number of ligaments. It is 
decidedly the most elastic of all the tissues of the human 
body. The movements of the cartilaginous pieces of the 
larynx vary the degree of tension of the vocal cords, and 
the transverse and oblique diameter of the glottis. In 
general, the latter becomes narrower when it emits sounds. 
The vocal cords, either as cords or as stretched membranes, 
attached at one side, evolve sounds when a column of air 
causes them to vibrate; and these sounds necessarily vary 
according to the tension and length of the cords, and the 
force of the current of air. A current of air traversing with 
a certain rapidity an orifice whose diameter is variable, may 
also, independently of the elasticity of the lips of the orifice, 
produce different sounds, as in the so-called wind musical 
instruments. The tube which rises above the glottis, and 
which consists of the ventricles, the pharynx, and the mouth, 
22 



338 VOCAL APPARATUS. LeCT. XVIII. 

may modify the intensity and even the tone of the sound 
produced in the glottis. Finally, we may consider the 
larynx as a cylindrical cavity, having two orifices in the 
centre of its bases. Assuming that a current of air tra- 
verses this cavity with different degrees of rapidity, that 
the diameters of these orifices are variable, and that the lips 
of its orifices, which are endowed with a variable tension, 
are elastic, we can easily conceive that a great variety of 
sounds may be produced by this apparatus. 

Analogy of the Organ of Voice to Musical Instruments. — 
These consideirations explain why the organ of the human 
voice, and the voice of animals, has been compared at one 
time to a s-tringed, at another to a wind instrument; some- 
times to a reed instrument; and, lastly, by Savart, to the 
bird-call. 1 must pass over in silence the long and minute 
explanation of the reasons assigned by the various authors 
in support of their different opinions concerning this organ. 
I do this the more willingly because I think we shall find, 
at the end of this lecture, that these theories of the voice 
are not so opposed to each other as their authors have 
imagined. 

Let UiS be guided, as usual, by experiment. All parts 
of the larynx may be removed without destroying the voice, 
provided that the vocal cords are preserved : these latter, 
then, are the indispensible elements of the apparatus ; and 
if we consider that they may undergo a more or less con- 
siderable degree of tension, by varying the opening left 
between their edges, we cannot but consider this essential 
part of the vocal organs as a reed instrument, with a mem- 
branous tongue of a peculiar construction. The other parts 
of the larynx, as well as the entire superior cavity of the 
mouth, form the pipe of the reed instrument; and the in- 
ferior part of the trachea constitutes the ordinary tube which 
proceeds, from th^ Uellows.. We are indebted to Weber,, 



LeCT. XVIII. REED INSTRUMENTS. 339 

but more especially to Miiller, for observations best fitted 
for demonstrating the correctness of this manner of view- 
ing the organ of voice in man. I shall endeavour to give 
you, as briefly as possible, an analysis of these investiga- 
tions. 

Reed Instruments, — Allow me first, however, to show you 
some general facts on sounds produced by reeds. When 
a rectangular metallic plate is fixed by one extremity, on 
the edges of an opening almost equal in extent to that of 
the plate, we have then a reed instrument, provided that 
the piece which contains the opening has a cylindrical or 
other form, and closes the orifice of a pipe into which a 
current of air is propelled. The mouth-harmonicon is the 
simplest instrument of this kind. A sound is also produced 
when a current of air is propelled by means of a tube, against 
a small metallic tongue fixed in some way, but not mounted 
on the chink. Some experiments seem to show that the 
pitch of sounds thus produced by these tongues, is inde- 
pendent both of the intensity of the current, and of the 
chemical nature of the air or gas: these circumstances 
merely vary the intensity of the sound. Some experiments, 
again, seem to have proved that, in order to vary the acuity 
and the gravity of a sound, the thickness of the tongues re- 
quires to be altered. We may explain in two different 
ways the sounds produced by a metallic tongue : it may be 
said, that the latter vibrates like an elastic rod, and that 
these vibrations are the cause of the sound ; or rather that the 
tongue, forced from the opening, in which it is fixed, by the 
current of air, returns to its former position in consequence 
of its elasticity ; and thus, by its position of equilibrium 
being disturbed, undergoes oscillations which give rise to 
impulses of the air, as in the sirene, or in Savart's machine. 
It must, however, be observed, that the sounds furnished 
when the tongue is made to vibrate by striking it, are never 



340 VOCAL APPARATUS. LeCT. XVIII. 

SO strong or so distinct as those produced by the impulse of 
a current of air. Hence, therefore, the second explanation 
of the sound of the tongue appears more probable than the 
first. It may, indeed, be replied, that by striking the 
tongue, we merely shake it, but not long enough to produce 
a uniform and durable vibratory movement. I do not, 
however, see why w^e should refuse to admit the simulta- 
neous existence of both these causes of sound ; for the 
tongue would easily, by its transversal vibrations, place 
itself in unison with the sound produced by the vibrations 
excited in the air. 

When a sounding tube is added to the reed, we have a 
reed instrument such as is generally met with; and sounds 
thus obtained are very different, both in tone and intensity, 
from those produced by the [reed or] tongue alone. The 
sound is neither that of the reed nor of the tube alone; but 
both become modified, and accord together. I must here 
explain to you the results obtained by Weber upon this 
subject. The pipe added to the reed may render the sound 
of the latter more grave, but never more acute; and the 
lowering of the pitch thus produced never exceeds an oc- 
tave. By lengthening the tube, we may again raise the 
sound to the fundamental primitive pitch of the reed ; and 
by increasing still farther the length of the tube, the pitch 
again becomes lowered ; but for this purpose it should be 
shorter than the first time. The length which it is neces- 
sary the tube should have, in order to lower the pitch to 
any given point, constantly depends on the relation which 
exists between the number of the vibrations which the reed 
and the tube separately make : thus the sound sinks gradu- 
ally as the tube is lengthened, until the column of air 
reaches such a length that it alone would produce the same 
fundamental sound as the reed itself would give. By again 
lengthening the tube, the sound sinks to about a fourth, 



LeCT. XVIII. REED INSTRUMENTS. 341 

until its length is double that of the column of air, which 
would give the same sound as the reed. At this point the 
pitch again rises to the fundamental note of the latter. 

Let us now devote our attention to the sounds of mem- 
branous reeds, and especially of those which, by their 
shape, have great analogy with the glottis, and which con- 
sist of a lamina of caoutchouc, having an opening in their 
middle, and which are fixed at the edges of a tube, into 
which the air is propelled. It is wuth apparatus of this sort 
that attempts have been made to construct an artificial 
larynx. Let us confine ourselves to the determination of 
the differences which exist between membranous and me- 
tallic reeds. Membranous reeds produce sounds which 
may be greatly modified, by varying their tension. By 
compressing the membrane, the sound becomes more acute. 
The principal difference in these two cases consists in this, 
that membranous reeds produce sounds which are more 
acute, in proportion as the force of the blast in the tube is 
greater ; whilst the reverse holds good with metalHc reeds. 
Miiller has endeavoured to determine what influence is ex- 
erted by the porte-vent and body of the tube adjusted on the 
membranous reed. But we must acknowledge, as does 
the author himself, that this subject has not hitherto been 
satisfactorily elucidated. The modifications produced in 
the sounds of the reeds, by the adjustment of a tube or 
porte-vent, are considerable. Experiments prove that, ac- 
cording to the lengths given to them, the sound is at one time 
raised, at another lowered. I shall relate to you one of the 
numerous experiments of Miiller : wdth a tube of 6 inches 
in length, the fundamental sound w^as re 4 ; this became 
mi'diese 4, w^hen a tube of 4 inches was added below the 
tongue ; and with a tube of 4J inches it rose to re-diese 4 ; 
with a tube of 8J inches it fell to ut-diese 4, and rose again 
to re 4 with a tube of 21 h inches. 



342 VOCAL APPARATUS. Lect. XVIII. 

The apparatus with membranous reeds constitutes the 
largest number of wind instruments ; and we must include 
among them the trumpet and French born. Indeed, an 
experienced performer embraces three octaves by merely 
varying the tension of his lips, without modifying the length 
of the column of air. 

The Human Vocal Organ is a Reed Instrument, — I believe 
that these introductory observations respecting membranous 
reeds, will enable you to form a clear notion of the pro- 
duction of the human voice. The organ is essentially a 
reed-apparatus, formed by two membranous lips. 

Miiller'^s Experiments. — The experiment of Miiller, which 
I am about to quote, will render this conclusion evident : 
He fixed the larynx of a human subject upon a board, 
after having removed all the parts above the inferior liga- 
ments. Then, by means of a hook, he attached a thin 
cord to the angle of the thyroid cartilage^ immediately 
above the vocal cords» The string passed over a pulley, 
and was connected with a scale, loaded with weights. By 
employing different weights, the cartilage was pulled, and 
the vocal cords stretched. A wooden tube was introduced 
into the trachea, to blow through. The following are the 
principal results which Miiller obtained with this appara- 
tus : — 

1st. When the glottis was sufficiently narrowed, and the 
inferior ligaments stretched, he obtained clear and full 
tones, which approximated to those of the human voice. 
An artificial larynx, made either with bands of the mid- 
dle coat of arteries, or with caoutchouc, yields similar re- 
sults. 

2d. By altering the tension of the vocal cords, the notes 
rise with the tension to an extent of about two octaves ; 
and when the tension is very considerable, the sounds be- 
come disagreeable and whistling. 



LeCT. XVIII. QUALITIES OF THE VOICE. - 34p, 

3d. Sounds produced when the vocal cords are but 
slightly stretched, differ in their intensity, but not in their 
tone, according as the glottis is more or less contracted ; 
when the vocal cords touch, the sound is as strong and as 
full as it can possibly be. 

4th. If the force of the current of the air be increased, 
the tension of the vocal cords remaining equal, the sound 
rises a fifth, or even more. 

5th. The parts of the larynx, and all the rest of the tube 
situated above the vocal cords, seem to act in the appa- 
ratus of the human voice, like tubes adjusted upon the 
reeds ; and we remark in the whole, that possibility of 
compensation which is always desired in musical instru- 
ments, and by means of which the tones remain the same, 
notwithstanding great differences in the intensity of the 
cause of sound. 

Compensation, — Weber discovered a method of con- 
structing a compensating reed-tube, in such a way that the 
sound has always the same purity for the piano as for the 
fortej notwithstanding the great changes in the force of the 
blast. The note of a reed-pipe may be raised by increasing 
the force of the current of air, and may be lowered by 
means of the tongue. Hence, we may conceive the pos- 
sibility of compensating these effects by means of a certain 
length of the column of air. 

Qualities of the Voice. — As for i\ie force or strength of the 
voice, it evidently depends in part on the aptitude of the 
vocal cords for vibration ; and, in part, on the fitness of 
the membranes and cartilages of the larynx, as well as 
of the pectoral, nasal, and buccal cavities, for resonance. 
The peculiar timbre of voice, which each person possesses, 
and its imperfections, evidently depend on the differences 
of these resonances, or on different aptitudes for vibration 
which the parts of the organ possesses. The intensity of 



344 VOCAL APPARATUS. LeCT. XVIII. 

the voice, or, as it is generally called, the volume of the 
voice, results, in part, from the force with which the air is 
driven from the lungs, and from the size of the thoracic 
cavity ; and in part, from the facility with which the vocal 
cords and the other parts of the larynx are able to vibrate. 
These modifications explain the difference which exists be- 
tween the male and female voice. To the great resound- 
ing cavities in the communication with the larynx, must be 
attributed the faculty which several species of monkeys have 
of giving vent to very shrill and deafening cries. 

Superiority of the Human Vocal Organ. — In reflecting 
upon all that we have said while studying the human voice, 
we cannot withhold our feeling of admiration at the wonder- 
ous skill displayed in the construction of the organ producing 
it. No instrument which we possess approaches it in per- 
fection. Some wind instruments can only run the octave, 
and pass without gradation from one note to another ; while 
in stringed instruments it is impossible to prolong the sound. 
The organ with two registers, which is formed both wuth 
reed-pipes, and mouth-pipes, gives sounds which resemble 
somewhat those of the human voice ; but these advantages 
are only obtained by means of a great number of tubes, and 
much complication. In the vocal organ, on the contrary, this 
infinite variety of sound is obtained by means of a very 
simple apparatus. 

Artificial Larynx. — I have seen in the museum of King's 
College, London, a caoutchouc larynx, modelled from a 
human larynx, to the different parts of which threads are 
attached, in order to enable its walls to be stretched more 
or less at pleasure, and to vary the capacity of the tube. By 
means of a current of air, the force of which can be mo- 
dified, a certain number of sounds are obtained which, for 
their timbre and purity, closely resemble those of the hu- 
man voice. 



LeCT. XIX. HEARING. 345 



LECTURE XIX. 



HEARING. 



Argument. — Modes of exciting the sensation of sound. Structure of the 
ear. Propagation of sonorous waves through the organ of hearing. 
Uses of the various parts of the ear. Physical properties of sound. 

A LUMINOUS sensation is the invariable effect of any 
excitation of the retina or optic nerve ; and, in like manner 
excitation of the acoustic nerve, however it may be effected, 
always gives rise to the sensation proper to this nerve. 
Thus, when speaking of electricity, I told you that a pecu- 
liar sound was heard when one of the poles of a voltaic 
pile was applied to the ear, the circuit being closed. Some 
substances, principally narcotics, when introduced into the 
organism, also produce sensations of sound. 

In most cases, however, sound is produced by vibratory 
movements, communicated to elastic bodies, and propa- 
gated, by means of the air or other media, to the acoustic 
nerve. In this way the function of hearing is usually 
exercised. 

In special treatises on Acoustics, experiments are de- 
scribed which tend to show^ that the cause of sound, the 
difference between grave and acute tones, and the intensity 
and timbre of sound, depend on the velocity and amplitude 
of these vibratory movements. In that department of physi- 
cal science, you will also find laid down the laws of the 
propagation of vibrations in air, liquids, and solids. We 



346 



HEARING. 



Lect. XIX. 



must, however, presume, that you have already acquired 
this knowledge ; and we purpose devoting the present lec- 
ture to the study of the sense of hearing, and more especially 
of the propagation of the sonorous vibrations through the 
different parts of the ear. 

Structure of the Ear. — But we must not pass over in 
complete silence the structure of the ear, which varies 

Fig. 30. 




A diagram of the ear. p. The pinna, t. The tympanum. I. The labyrinth. 1. 
The upper part of the helix. 2. The antihelix. 3. The tragus. 4. The anlitragus. 
.5. The lobuliis. 6. The concha. 7. The upper part of the fossa innominata. 8. The 
meatus. 9. The membrani tympani, divided by tiie section. 10. The three little 
bones, crossing the area of the tympanum, malleus, incus and stapes ; the foot of the 
stapes blocks up the fenestra ovalis upon the inner wall of the tympanum. 11. The 
promontory. 12. The fenestra rotunda; the dark opening above the ossicula leads 
into the mastoid cells. 13. The Eustachian tube ; the little canal upon this tube 
contains the tensor tympani muscle in its passage to the tympanum. 14. The vesti- 
bule. 15. The three semi-circular canals, horizontal, perpendicular, and oblique. 
16. The ampullae upon the perpendicular and horizontal canals. 17. The cochlea. 
18. A depression between the convexities of the two tubuli which communicate with 
the tympanum and vestibule; the one is the scala tympani, terminating at 12; and 
the other is the scala vestibuli. 



LeCT. XIX. HEARING. 347 

extremely in different animals. In some it is reduced to 
an apparatus of the greatest possible simplicity ; namely, to 
a special nerve, whose peripheric extremity is expanded in 
a liquid contained in a cavity of variable form, situated 
sometimes in the osseous wall of the skull, sometimes hav- 
ing membraniform envelopes. We shall give a particular 
description of the human ear, because it is to this that we must 
devote our especial attention, on account of its complication 
and perfection. 

The exterior part of this organ, called the pinna or auri- 
cle of the ear, is of a fibro-cartilaginous nature, very pliant 
and elastic, and has the greatest portion of its surface free. 

It is, in a manner, an expansion of the external auditory 
passage. The form of the pinna varies greatly in the higher 
animals: thus, in man, although it presents a number of 
folds, we may consider it as normally implanted in con- 
nexion with the auditory tube. In the horse, the ass, &c., 
it consists of a species of cone, which arises from this tube. 
In these animals the pinna is generally moveable ; whilst in 
man its motions are very limited. 

The external auditory passage, or meatus auditorius exter- 
nus, excavated in the temporal bone, terminates at a short 
distance from the surface, where it is truncated obliquely 
to its axis. A thin, and very elastic membrane, called the 
membrane of the tympanum, closes the passage. The tym- 
panum is a cavity, in great part osseous, which has five 
openings: one formed by the extremity of the external 
auditory passage, and closed by the membrane of the tym- 
panum; two opposite to this, one situated above and called 
the oval window (fenestra ovalis,) and the other the round 
window (fenestra rotunda ;) both openings are closed by 
membrane. Superiorly and posteriorly the tympanum com- 
municates by a large irregular opening wath the mastoid 
cells. Lastly, in the lower part of the tympanum there 



348 HEARING. LeCT. XIX. 

exists a fifth opening, namely, that of the Eustachian tube, 
which communicates with the upper part of the pharynx. 

Within and across the tympanum is fixed a chain of small 
bones ; which from the analogy of their forms, are called 
the hammer (malleus,) the anvil (incus,) the orbicular hone 
(os orbiculare,) and the stirrup (stapes.) The hammer is 
attached parallel to the membrane of the tympanum, like a 
solid ray going from the circumference to the centre 
of the latter. One extremity touches the anvil, which is 
connected with the orbicular bone, and the latter with the 
stirrup, w^hich terminates at the fenestra ovalis. Several 
muscles eflfect slight movements in the chain, shortening 
and lengthening it, and thus varying the degree of tension 
of the membranes upon which it presses. 

Beyond, or on the inner side of the tympanum, in the 
substance of the petrous bone, is situated what is called the 
labyrinth^ or internal ear ; formed of different cavities, which 
communicate with each other, and are distinguished by the 
names of the vestibule^ the semi-circular canals^ and the 
cochlea. The vestibule occupies the central part, and com- 
municates with the tympanum by the fenestra ovaHs, and 
with the three semicircular canals, which are expanded at 
their extremities, forming ampullae. The cochlea, so-called 
because it is curved spirally, like the shell of a snail, com- 
municates with the interior of the vestibule, and is sepa- 
rated from the tympanum by the fenestra rotunda. The 
vestibule and the cochlea contain a fluid called the liquor 
of Cotunnius, in which float the filaments of the acoustic 
nerve. Such is a succinct enumeration of the principal 
parts of the ear of man, and the higher animals. We shall 
examine the propagation of the sonorous waves through 
these parts, in order to deduce therefrom the physical 
theory of hearing. 

Propagation of Sound through the Ear. — The ear is com- 



LeCT. XIX. PROPAGATION OF SOUND. 349 

posed of several membranes, of osseous parts, of air, and 
of a liquid. The vibrations are propagated through these 
bodies, all of which transmit sound in consequence of the 
vibratory state excited in them by that of sonorous bodies. 
Each portion of the ear thus takes part in the function which 
this organ has to fulfil. But in what manner do the diffe- 
rent parts act ? Acoustics cannot give a completely satis- 
factory reply to this question ; but by the aid of compara- 
tive anatomy, of experimental physiology, and of pathology, 
we may succeed in determining the different degrees of im- 
portance possessed by each part in the function of hearing, 
and,'hence, can determine in what degree they respectively 
contribute to the perfection and delicacy of the ear. The 
external and middle parts of the ear are wanting in a great 
number of animals, which, nevertheless are considered to 
be endowed with a perfect sense of hearing. Thus, in 
birds there is no vestige of the pinna; in reptiles the ex- 
ternal auditory passage is wanting; and in fishes the ear is 
reduced to the internal part alone. But the part which is 
present in every case, in which hearing can be effected, is 
the vestibule ; in other words, a membranous sac, filled 
with a liquor in which the extremities or ramifications of 
the auditory nerve are contained. Any other mode of ter- 
mination of this nerve would have been less advantageous 
for the exercise of this faculty. The nerve being reduced 
to some very small filaments, diffused in a liquid, the points 
of contact are in this way multiplied as much as possible. 
The structure of the nerve thus approaches more to that of 
the liquid in which it is placed. These ramifications, scat- 
tered in the fluid mass, are expanded in every direction, 
and are thus directed normally with their extremities to- 
wards the vibratory movements, which are propagated to 
the fluid by the walls of the spherical cavity in which it is 
contained. We know that vibrations are propagated in 



350 HEARING. LecT. XIX. 

liquids, as in membranes and in all elastic bodies, which 
divide into vibrating parts separated by nodal lines. In 
liquids, numerous vibratory movements can likewise be 
propagated, and co-exist without interfering with one 
another. Some experiments of Cagnard-Latour, seem also 
to prove that vibrations are propagated more readily from 
the solid walls of a cavity to the liquid contained in it, if 
small solid bodies are dispersed through the latter, either 
floating or fixed to the walls. The points of contact be- 
tween the solid and the liquid are thus rendered more nu- 
merous, and the directions in which the vibrations can be 
propagated, in a direct line from one to the other of these 
media, are multiplied by the inequalities presented by these 
surfaces. These small solid bodies are met with in the li- 
quid which fills the labyrinth of the ears of certain fishes. 
We may, therefore, conclude, that the vestibule, or more 
particularly the mode in which the acoustic nerve termi- 
nates in all animals, is of great importance in the function 
of hearing, and is explicable by the laws of acoustics. 

The undulations of the air, produced by a sonorous body, 
may excite the auditory nerve, by being transmitted either 
through the osseous parts of the skull in which the air is con- 
tained, or through the column of air contained in the exter- 
nal auditory passage. If we carefully close the external 
auditory passages, we can still hear very well the tick- 
ing of a watch, held between the teeth, or applied to any 
part of the head. Some persons afflicted with hardness of 
hearing, manage to hear distinctly by applying to the audi- 
tory passage, or by holding between the teeth, a wooden 
rod fixed to the centre of a reservoir of air, placed in front 
of the sounding body. The stethoscope employed by phy- 
sicians acts principally as a solid cylinder, by which a great 
number of points of contact are established between the 
sounding body and the ear applied to it. 

The column of air contained in the external auditory pas- 



LeCT. XIX. PROPAGATION OF SOUND. 351 

sage, also vibrates in consequence of the sonorous undula- 
tions excited in the air. Experiment proves, that a sound 
produced in a solid body is much more distinct to our ear 
if transmitted by means of a solid immediately in contact 
with the ear, or through the intervention of another similarly 
interposed body, all other conditions being equal. If, on 
the contrary, the sound be produced by sonorous undula- 
tions primarily excited in the air, as in all wind instruments, 
it becomes the more distinct in proportion as the quantity of 
air in communication with the auditory passage, is \vithin 
certain limits, more considerable. The ear-trmnpet acts on 
this principle. When these two modes of propagation are 
combined in the same organ, it cannot be doubted but that 
they powerfully concur in perfecting the function. These 
principles are applicable to the explanation of the use of 
the pinna, and of the external auditory passage. We per- 
ceive in these parts an instrument analogous to an ear- 
trumpet, which, by its peculiar form, collects and reflects 
towards the axis of the canal, a greater number of sonorous 
waves; and which, at the same time, acts like a reservoir 
of air, aud increases the sound. All stringed and wind in- 
struments yield a more intense sound by the effect of the 
presence of this reservoir. Savart's bell, which, after having 
been put in vibration, is brought near an air receiver, and 
the monster tuning fork of Marloye, placed on a large air- 
chest, place beyond doubt the effects produced by the re- 
sonance of masses of air which surround sonorous bodies. 
An analogous experiment can be made by bringing a tuning 
fork near to the ear, or introducing it within the mouth : in 
the latter case, the sound acquires a great intensity. In all 
these instances, the sound is augmented by sonorous waves 
reflected by the w^alls of the receivers; and, at the same 
time, by vibrations communicated to the mass of air, and 
to the walls of the reservoir. In all cases, however, it is 



352 HEARING. LeCT. XIX. 

essential that all should vibrate in unison with the primitive 
note, in order that the sound should be increased. 

In animals in which the pinna is moveable, the analogy 
of this part of the ear with the ear-trumpet is very evident. 
Thus we see the animal, when pursued, direct the opening 
of the pinna backwards ; and, on the contrary, when pur- 
suing its prey, it turns the same part forwards. In man 
these movements are wanting ; and the external form of his 
ear is also very different from that of other animals. Hence, 
it is difficult for us to understand the use of the pinna, and 
we might quote a number of instances in which hearing 
has been but very slightly affected by its absence. Con- 
sidering man's usual position, and the mobility and ele- 
gance of his head, it does not appear possible to endow 
the pinna with the power of motion without giving to this 
organ the shape of an ear-trumpet; and all of you I suspect, 
would be shocked at the idea of being thus transformed into 
a kind of mythological monster. Let us add, that for the 
same reasons, the pinna could not be mobile. So far from 
this, it is formed of an elastic cartilage, the plane of which 
is for the most part parallel to that of the membrane of the 
tympanum ; and, consequently, normal to the axis of the 
external auditory passage. According to the laws of the 
propagation of vibratory movements, this is the best ar- 
rangement it could have for receiving the sonorous undula- 
tions, which, thus striking this membrane perpendicularly, 
are propagated more readily into the interior of the ear, 
either by the solid walls of the auditory passage, or by the 
column of air which it contains. It is well known that 
when we wish to hear distinctly, we place the head in such 
a position that the pinna receives the sonorous waves nor- 
mally. By the vibrations which sound excites in the ex- 
ternal membrane of the ear, or by those produced in the 
column of air contained in the auditory passage, the vi- 



LeCT. XIX. PROPAGATION OF SOUND. 353 

bratory movement reaches the membrane of the tympanum, 
which is stretched over the internal orifice of this tube. 
Why, it may be asked, has the tympanum been added ? 
Why is not the apparatus so arranged that the vestibule or 
sac, in which the acoustic nerve is contained, should be in 
contact with the membrane of the tympanum ? We have 
no hesitation in replying that hearing could be effected 
without this tympanum, as is the case in species of ani- 
mals ; and, as has been said, with some men, in whom 
this middle ear has been deficient, either from disease or 
from natural conformation. It is obvious, however, on 
physical grounds, that the middle part of the human ear 
renders this organ more perfect and less exposed to un- 
dergo alterations. 

Let us, in the first place, speak of the manner in which 
membranes vibrate. Savart has shown that, when they are 
properly stretched, or put in proximity with an organ pipe, 
or any stringed instrument producing a sound,, they vi- 
brate as if they were in contact with the sonorous bodies ; 
and if they be covered with sand, we obtain the division 
of these membranes into vibrating parts, separated by the 
ordinary nodal lines. At each variation of sound, new 
arrangements appear upon the membrane, and these di- 
visions are more easily and quickly produced upon mem- 
branes than upon plates of metal or glass. Savart has 
likewise shown, that membranes alone present the pecu- 
liarity of dividing in different ways under the influence of 
the same sound ; all of them having the same form, di- , 
mension, and tension. Lastly, we may add, that by vary- 
ing the degree of tension of a membrane, its manner of 
dividing and vibrating for the same sound, is changed. 
From all these facts, for which we are indebted to Savart, 
we may infer that, in order to propagate sound in the inte- 
rior of the ear, and in order to modify at pleasure the in- 
23 



354 HEARING. LeCT. XIX. 

tensity of the vibratory movements, it is useful to close the 
auditory passage with a tense membrane, and to add to the 
interior of the organ an apparatus adapted for propagating 
vibrations to parts in contact with the acoustic nerve, and 
which, at the same time, can at will vary the tension of the 
membrane of the tympanum. 

Here is a common ear-trumpet, on the aperture of which 
is fixed a membrane ; upon this membrane a small wooden 
rod is glued, as in the experiments of Savart and Miiller. 
By means of this, the tension of the membrane can be 
easily altered. If I listen to a sound by applying the trum- 
pet to my ear, I perceive a great difference in its intensity, 
according as the membrane is rendered more or less tense : 
when it is very much so, the sound is remarkably weaker 
than that obtained by relaxing the membrane. In the first 
case, perhaps, the membrane is more easily divided into 
vibrating segments, which produce sounds in unison with 
the primitive note, but not so strong. In the human ear 
we can vary the tension of the membrane in two different 
ways : either by the chain of ossicles (the effect produced 
by the wooden stick in our preceding experiment ;) or by 
modifying the density and elasticity of the air contained in 
the tympanum. This latter method, which is not the natu- 
ral one, could only be effected by a certain degree of dex- 
terity, and by making a violent effort. It is important, 
then, to have in the middle ear a free and constant com- 
munication between it and the exterior air : this is the office 
of the Eustachian tube, which opens at one extremity into 
the tympanum, and at the other into the fauces. In this 
way the air of the tympanum has a constant degree of 
moisture, while its elasticity is the same as that of atmos- 
pheric air. The physical properties of the membrane of 
the tympanum, as well as of the membranes of the fenes- 
trse, rotunda, and ovalis, are thus preserved. . 



LeCT. XIX. PROPAGATION OF SOUND. 355 

If we close the nose and mouth, and then enlarge, as 
much as possible, the thoracic cavity, we produce a tem- 
porary deafness ; and the same effect is obtained by means 
of a strong and sustained expiration. This deafness con- 
tinues for a few seconds, and is most effectually got rid of 
by an act of deglutition. In the one case, the air of the 
tympanum is less dense ; in the other, more dense than the 
exterior air ; while the membrane undergoes a different 
tension in the two cases, — in the one being drawn inwards, 
in the other being forced outwards. Wollaston, who first 
observed these facts, remarked that in the first case he was 
deaf to grave sounds ; while, in the other case, he was deaf 
only to acute ones. Thus he states that he could not hear 
distinctly the loud noise of a carriage at a certain distance, 
though he readily heard the noise produced by striking 
the end of the nail upon a table. I think I have given 
a sufficiently plausible reason for this difference. An expe- 
riment analogous to the preceding one, may be made by 
aieansof a trumpet prepared with the membrane fixed over 
its opening. By rendering this very tense, all loud sounds 
were indistinctly heard, whilst, on the contrary, the ticking 
of a watch was rendered stronger. Cases are mentioned 
of individuals who cannot hear the ordinary voice, and who 
can only hold conversation in the midst of a great noise. 
In these cases it must be admitted, that the sensibility for 
grave and strong sounds may continue. This can be un- 
derstood only to a certain extent, by assuming that the 
membrane is deprived of the power of varying the tension 
under different circumstances. 

The internal muscle of the hammer (malleus) and that of 
the stirrup (.vto/jes) serve to modify the tension of the mem- 
brane of the tympanum, in obedience to the will. Miiller 
assumes that these muscles are excited to contract by a 
reflex action, as the muscular fibres of the iris are by a 



356 HEARING. LeCT. XIX. 

Strong light. Under the influence of a prolonged and vio- 
lent noise, the stirrup and the hammer, by contracting 
their muscles, render tense the membrane upon which they 
are fixed, and thus give rise to a temporary, and, under 
the circumstances, a useful deafness. 

What is the function of the entire chain of ossicles ? 
Why are there four connected bones together rather than 
a single one ? Why not suppress the foramen rotundum, 
or the foramen ovale, or even both of them, by applying 
the vestibule upon the membrane of the tympanum ? It 
is impossible, with our present acoustical knowledge, to 
answer these questions satisfactorily. The chain of ossi- 
cles, besides having the faculty of varying the tension of 
the membranes upon which its extremities are fixed, also 
fulfils in the ear the same office as the bridge in stringed 
instruments, and the cylinder of a drum. If we sprinkle 
sand on one of the membranes of a drum we observe 
that the sand vibrates, and forms itself into divisions when 
we make the other membrane sound ; and this propagation 
varies according to the arra^ngements of the cylinder. The 
chain of ossicle is a kind of ntusic-bridge suspended in the 
tympanum, which not only propagates the vibrations from 
one wail to the other, but receives also impulses of air upon 
the various parts of its surfac-e. The membrane of the fenes- 
tra ovalis, which communicates with the vestibule, where the 
nerve is, has its elasticity and tension better protected by 
being placed in an air cavity contained in the interior of 
the ear, than it would be if it were in direct contact with 
the atmosphere. It is, undoubtedly, for the purpose of 
giving to the ear a more varied and extended mode of ac- 
tion, that it is provided w^ith two openings, supplied with 
stretched membranes in the internal part of the ear, and in 
proximity with the acoustic nerve ; one of the openings 
being free, and the other in contact with the membrane of 



LeCT. XIX. PROPAGATION OF SOUND. 357 

the tympanum, through the intermedium of the chain of 
ossicles, and thus rendered susceptible of different de- 
grees of tension. We must thereby obtain a greater compass 
in the function of the ear. These replies to the questions 
which we put, doubtless, are not the only ones that we may 
one day be able to give ; but since the organ can exist 
and perform its function without this chain of ossicles, 
and without either the membrane or the tympanum, we 
must admit that these parts are not essential to the ear, 
and, that they serve only to render it more perfect, and for 
its conservation. 

I shall make but a few remarks on the semicircular ca- 
nals and the cochlea. It is generally supposed, that the 
vibration excited and transmitted through the solid walls, 
in which the ear is contained, are transmitted by these walls 
to the acoustic nerve. 

I shall rapidly pass over the physical characters of sound, 
the comparison of different sounds, and the limits of ap- 
preciable sounds. Any impulse or excitation communi- 
cated to the acoustic nerve, as mentioned at the commence- 
ment of this lecture, produces a sonorous sensation. By 
the word sound, we strictly understand a sensation which 
is preserved uniform for a certain time, and which is sus- 
ceptible of being measured and compared. Sound differs, 
then, from a mere noise, inasmuch as the latter is the effect 
of a single shock, or of a series of shocks which are re- 
peated without any regularity ; whilst the sonorous sensa- 
tion is that which we experience when the acoustic nerve 
receives a certain number of successive shakings, sepa- 
rated from each other by a certain and constant interval 
of time. It is this which takes place with Savart's wheel, 
with Cagnard Latour's sirene, or by vibrations of a stretched 
cord, producing corresponding undulations in the air which 
reach the ear and strike the acoustic nerve, producing a 



358 HEARING. LeCT. XIX. 

number of impulses in a given time which belong to the 
movements of the sonorous body. The acuity or gravity 
of a sound, is more or less due to the great rapidity with 
which the vibrations succeed each other. The intensity 
depends on the extent of excursions of the vibrating parts. 
Wollaston and Savart have endeavoured to determine 
the limits within which sounds remain perceptible, or cease 
to be so, to our ear, by acquiring too great an acuity or 
gravity. Savart showed, that these limits were much more 
considerable than had been previously supposed ; and that, 
in order to perceive, either very acute or very grave sounds, 
it is requisite merely to increase the intensity. By making 
a long bar of iron pass, with a certain rapidity, through a 
longitudinal chink, which it almost completely filled, we 
obtain a very intense sound when this bar goes and comes 
seven or eight times in a minute ; and, as at each passage 
of the bar there is a compression of the air, to which a 
rarefaction succeeds, the undulations which constitute the 
sound are only to the extent of forty or fifty per second. 
If, on the contrary, we employ a toothed wheel of very 
large diameter, and hold an elastic plate in contact with 
the teeth when the wheel is rotated, we perceive a very 
acute sound when it has twenty-four thousand impulses per 
second, in which case the sound is formed of forty-eight 
thousand undulations. How complicated must be the or- 
gan of hearing, when we reflect that its sensibility is pre- 
served within limits so far apart, and that its principal parts 
must vibrate in unison with sounds which vary from four- 
teen to forty-eight thousand vibrations per second. 

According to the definition given of sound, we explain 
without difficulty how it happens that, by the coexistence of 
two sounds, whose vibrations stand to each other in a sim- 
ple ratio, we hear a graver sound. When this takes place, 
there are some moments in which the shakings, produced 



LeCT. XIX. PROPAGATION OF SOUND. 

by the two sounds, coincide upon the acoustic nerve ; and, 
if these coincidences be sufficiently near and regularly re- 
peated, we have the sensations of a very grave sound. 
When these coincidences are very rare, which happens 
with sounds almost in unison with each other, we have no 
other sensation than that of the well-known phenomenon of 
beats^ observed for the first time by Tartini. 

Not being able to speak of all that relates to the act of 
conscience, awakened through the excitation of the acoustic 
nerve, I cannot stop at the theories of music. If the sounds 
that we hear simultaneously are, by the relative number of 
their vibrations, in simple ratio to each other, we then ex- 
perience those most agreeable sensations which we call 
harmonics ; and the contrary effect takes place when these 
relations do not exist. Experiment teaches us, that har- 
monic sounds are obtained simultaneously by touching a 
thick cord, extended so as to make it render the funda- 
mental sound due to the vibration of its entire length. We 
therefore conclude, that the cord divides itself into a certain 
number of parts, which vibrate separately and at the same 
time. We also know, that by having several cords to- 
gether, if their lengths are in simple ratios, it is sufficient to 
cause one to vibrate, in order that the others should render 
the sound proper to their lengths. We may therefore as- 
sume, that the membrane of the tympanum, the membrane 
of the fenestra ovalis, and perhaps, also, the extremities of 
the acoustic nerve, may be the seat of harmonic sounds ; 
and, that the elasticity of these parts is not opposed to these 
movements. The contrary should hold good for sounds 
which we call discords. 



360 VISION. Lect. XX. 



LECTURE XX. 

VISION. 

Argument. — Two parts or stag-es in the process of sensation, viz. the 
action of external agents, and the perception of impressions. 

Vision is effected by means of the physical agent called light. Necessity 
for an optical apparatus to form images of exterior objects. Three 
modes of forming images : the camera obscura; the mosaic dioptric in- 
strument; and the concentrating dioptric instrument. 

Structure of the human eye : its membranes and humours; dimensions of 
its various parts. 

Mechanism of vision. Action of the eye on the rays of light. Image 
formed on the retina. Adaptation of the eye to vision at different dis- 
tances : hypotheses to account for it : Sturm's explanation. Presbyopia 
and Myopia. Achromatism of the eye. Cause of erect vision with in- 
verted images. Idea of distance and size of objects. Single vision. 
Wheatstone's observations on binocular vision : his stereoscope. Dura- 
tion of impressions on the retina. Ocular spectra: accidental colours. 

Two Stages in Sensation.— Thu function of every appa- 
ratus of sensation is composed of two distinct parts : 

1st, external objects produce in the sensorial nerves a 
modification which is peculiar and specific for each sense ; 

2dly, this modification is transmitted to the brain, where 
the impression is received and transformed into a perception 
of the external object. 

Causes of Vision. — In vision, as in bearing, our relations 
to external objects are the same. When the sun rises above 
the horizon and we see it, there necessarily exists some sen- 
sible relation between that luminary and our eyes. It must 
be by the physical agent called light, that the sun produces 



LeCT. XX. CAMERA OBSCURA. 361 

an impression on our eyes. In this lecture we shall examine 
the way in which the rays of light, emanating from external 
objects, reach the retina and excite it. 

If, in the dark, you press or strike the eye, a vivid, but 
indistinct luminous sensation is produced. If the pressure 
be made by means of a small body on a limited extent of 
the eye, the sensation w^ill be equally limited, and you will 
be conscious of its limit; that is the degree of pressure ex- 
ercised upon the compressed point. 

Optical Apparatus required to form Images. — If the sur- 
face of the retina were presented naked to the luminous ob- 
ject, without any optical apparatus being placed in front of 
it, it is obvious that every point of it would be stimulated 
at the same time, by all the rays which proceed from the 
object in every direction. And if thousands of those rays, 
with their divers colours, simultaneously presented them- 
selves before the eyes, they would all at the same time give 
rise to the impression of their light upon the retina, which, 
however, would not have an exact and definite sensation of 
any of them. 

The problem to solve to obtain vision, consisted, there- 
fore, in placing before the retina an optical apparatus by 
which the rays of light, emanating from the various parts of 
an object, should separately reach distinct parts of the re- 
tina, and in a given order. 

1. The Camera Obscura. — The camera obscura is the 
most simple apparatus which we possess for obtaining these 
effects. Fancy a diaphragm w^ith a small aperture in its 
centre, placed before the retina : the rays proceeding from 
one extremity of the object, passing through the aperture, 
will excite a certain point of the retina; and the same will 
take place with all the other parts of the same object, w^hich 
will excite a corresponding number of parts of the retina. 
The smaller the aperture, the more defined will be the 



362 VISION. Lect. XX. 

image, but its light will be proportionately fainter: this, 
perhaps, is the reason that, in nature there is no apparatus 
for vision analogous to the camera obscura. 

2. The Mosaic Dioptric Instrument. — Miiller has described 
a very curious arrangement found in the eyes of some insects. 
Imagine that in front of the retina, and perpendicularly to 
its surface, there is placed an immense number of small 
cones filled with a transparent matter, and whose sides are 
invested by a black and opaque pigment, capable of ab- 
sorbing all the rays which do not traverse the cone in a 
direction parallel to its axis. A transparent and convex 
membrane forms the external surface, which is also the base 
of the cone. In the summit or apex of the cone is fixed 
the extremity of the nervous fibre, which, according to 
Wagner, is prolonged into the interior of the cones, on 
whose sides it is expanded. It is easy to conceive how 
distinct vision may be obtained by means of this arrange- 
ment. Of all the luminous rays which emanate in every 
direction from an object, and fall upon every point of the 
surface of the eye, those only which proceed from a deter- 
minate point of the object, and which traverse one of the 
cones parallel to its axis, can reach the retina. The dis- 
tinctness of the image will depend, then, on the number of 
cones arranged on the nervous surface ; whilst the intensity 
of the image must always diminish with their number. We 
can also understand how, with this apparatus, the extent of 
the field of vision may be increased, by augmenting the 
convexity of the spherical segment representing the eye. 

3. The Concentrating Dioptric Instrument. — Lastly, to 
obtain an apparatus of vision still more perfect than the one 
just described, it was necessary so to construct it that the 
distinctness of the image should not be obtained at the ex- 
pense of its brightness; and, that rays which fall very 
obliquely on the surface of the eye should be made to con- 



LeCT. XX. STRUCTURE OF THE HUMAN EYE. 



363 



verge upon the retina. Such is the construction of the eye 
of man, and of all the higher animals. 

Structure of the Human Eye. — Let us now describe the 
form of the eye, and of the parts composing it. This organ 
is contained in a cavity called the orhit. Its form which is, 
almost spherical, is preserved by an exterior coat formed of 
a fibrous dense membrane, which, at its posterior part, is 
opaque, and is called the sclerotic coat^ or the opaque cornea; 
but at its anterior part is transparent, has an augmented 
curvature, and takes the name of the transparent cornea. 

In the circle formed by the junction of the transparent 
with the opaque cornea, is extended and fixed an opaque 

Fig. 31. 




A Longitudinal Section of the Globe of the Eye. 



1. The Sclerotic Coat. 

2. The Cornea. 

3. The Choroid Coat. 

4. The Ciliary Ligament. 

5. The Ciliary Processes. 

6. The Iris. 

7. The Pupil. 

8. The Retina. 

9. The Canal of Petit, which encircles 
the Lens. 



10. The Anterior Chamber of the Eye, 
containing the .-Aqueous Humour. 

11. The Posterior Chamber. 

12. The Lens enclosed in its proper 
Capsule. 

13. The Vitreous Humour enclosed in 
the Hyaloid Membrane. 

14. A Tabular Sheath of the Hyaloid 
Membrane. 

15. The Neurilema of the Optic Nerve. 

16. The Arteria Centralis Retinae. 



membrane called the iris^ w^hich gives the colour to the 
eye, and is composed of muscular fibres, one portion of 



364 VISION. Lect. XX. 

which is circular, while the other radiates from the centre 
to the circumference. In its centre, the iris is pierced by 
a circular opening called the pupil^ whose diameter is vari- 
able according to the intensity of the light. Behind the 
iris is placed the crystalline humour or lens, a solid, lenti- 
cular, transparent body, invested by its own proper mem- 
brane. On the internal surface of the sclerotic, is a dark 
membrane called the choroid: this is lined by another, termed 
the retina, which is semi-transparent and thin, and is formed 
by the expansion of the medullary portion of the optic nerve 
placed at the bottom of the orbit. The eye is divided by 
the crystalline lens into two distinct portions. The anterior 
one, in which the iris floats, is filled with a liquid called 
aqueous humour, which is very similar to water, and con- 
tains traces of common salt. The posterior part contains 
a much denser liquid termed the vitreous humour. When 
carefully examined, the crystalline is found to consist of 
concentric layers, whose consistence and refracting power 
increase from the circumference to the centre. Lastly, the 
line, according to which the axis of the figure of the eye is 
directed, in the act of distinct vision, is called the optic axis* 
The following are the mean dimensions of the different 
parts of the human eye: — 

Radius of curvature of the sclerotica - 
Radius of curvature of the transparent cornea 
Diameter of the iris ... 
Diameter of the pupil - - - 

Thickness of the transparent cornea 
Distance of the pupil from the cornea 
Anterior radius of the crystalline lens 
Posterior radius of the crystalline lens 
Diameter of the crystalline lens 
Thickness of the crystalline lens 
Length of the optic axis 



Millitnetres. 


10 to 11 


7- 


• 8 


11- 


12 


3- 


7 


1 




2 




7 — 


8 


5 — 


6 


10 




5 




22- 


24 



LeCT. XX. ACTION OF THE EYE ON LIGHT. 



365 



The numbers which represent the indices of refraction 
for the media of the eye, are as follows: the index of re- 
fraction of the aqueous humour differs but little from that of 
water, which is 1-336 ; that of the aqueous humour is 1-337; 
of the vitreous humour 1-3394; of the surface of the crys- 
talline lens 1-3767; of the centre 1-399 ; and the mean, 
1-3839. 

Eyes of other Animals. — Some differences are observed 
between the eyes of animals and those of man. In some 
birds, the crystalline is almost spherical ; and, in all, the 
transparent cornea is very convex. In fishes, on the con- 
trary, the cornea is almost plane. The choroid^ also, pre- 
sents very different colours in different animals. 

Action of the Eye on Light. — Although the descrip- 
tion of the eye, which I have here given you, is as sum- 
mary as possible, yet, by its aid, I trust that you will easily 
comprehend, in a general way, the progress of the rays of 
light through the eye, by considering that this organ is con- 
Fig. 32. 




Diagram explanatory of the Mechanism of Vision. 



stituted by a system of spherical lenses, which produce the 
convergence of the luminous rays. 

Most of the rays of the luminous cones emitted by the 



366 VISION. Lect. XX, 

points A and b of the object, transverse the transparent cor- 
nea c c, and enter the aqueous humour contained between 
the cornea and the surface of the crystalline lens : they 
thus undergo a first refraction, bending towards the rays 
which enter parallel to the axis of the eye. It is easy to 
calculate the convergence of these rays, when the convexity 
of the cornea, and the refracting power of the aqueous 
humour, have been ascertained. These rays arrive at the 
crystalline, which is a real double convex lens, and suffer 
here a further deviation and inclination towards the axis of 
the eye. Lastly, they undergo a third refraction in the 
same direction, when passing out of the crystalUne lens, 
and at the moment of their entrance into the vitreous hu- 
mour. The route followed by the rays emanating from a 
and B is indicated in figure 32: their focus is at a and h: and, if 
F be the retina, a and h correspond to points a and b 
of the object. If we suppose the retina at h or at g, the 
points c and y, as w^ell as e and o, will be the circles in 
which the image of a and b will be diffused. Vision, 
therefore, is distinct when the retina is exactly at such a 
distance from the crystalline lens, that the focus of the rays 
is formed upon it. But in order to obtain this result, it is 
necessary to intercept all the rays which would fall near 
the margin of the crystalline, and which would have their 
focus at a different point from that of the rays which tra- 
verse the central part of the lens. This is the most im- 
portant function of the iris and the pupil, which produce 
the effect of a diaphragm, provided with an opening sus- 
ceptible of great variations in its diameter. For the same 
purpose, the crystalline should be denser and more convex, 
in proportion as the medium in which vision is effected is 
denser ; as is the case with fishes. 

Lastly, the \vhole internal part of the eye, and espe- 
cially the posterior surface of the retina, is covered with a 



LeCT. XX. SEAT OF THE IMAGE FORMED. 867 

black pigment, which absorbs all the rays, which would 
otherwise be again reflected within, and thus disturb the 
distinctness of the image. All optical instruments have this 
arrangement : thus, the tubes of telescopes and of micros- 
copes are blackened in the interior. 

Seat of the Image formed. — A very simple experiment 
serves to show that images are formed at the bottom of the 
eye, upon the retina. It consists in placing, in a dark 
room, the eye of an Albino rabbit before the flame of a can- 
dle placed at a proper distance : as the sclerotica in these 
eyes is semi-transparent, w^e can distinctly see the image of 
the flame inverted upon this membrane. Here is the eye 
of an ox, whose sclerotica has been pared and rendered 
almost transparent : each of you can see the image of the 
flame, which I hold before it, inverted upon this membrane. 
If we calculate by means of the formula for convex lenses, 
taking into consideration the dimensions and refracting 
powers of the different parts of the eye, we find that if an 
object be placed at about 30 centimetres [11*8 English 
inches] from the eye, its rays at this distance fall upon 
the eye with the necessary degree of divergence for them 
to converge to a focus upon the retina. From all this, 
therefore, it is natural to conclude that vision, that is, the 
sensation of a body which transmits luminous rays to our 
eye, is owing to the modification effected in the retina by 
the luminous rays brought together upon all the points o^ 
this membrane, where the image of the body is formed ; 
and to the transmission of this modification to the seat of 
perception, by means of the optic nerve. In whatever way 
the retina is excited, the sensation experienced is always 
that of light: thus the passage of electricity, a blow^, and 
pressure of the eye, and, consequently, that of the retina, 
produce luminous impressions there; so that the nerves 
of the senses, when excited, are each susceptible of ope 



368 VISION. Lect. XX. 

determinate kind of sensation only. The retina, upon 
which images of luminous objects are formed, is less en- 
ergetically affected by points whose light is less intense ; is 
more affected by the more illuminated points, and is unaf- 
fected by the dark points. If images were not formed upon 
the retina, and if the eye was composed of this membrane 
only, without the apparatus of lenses, vision could not be 
distinct: all would be reduced to distinguishing the alter- 
natives of day and night, of light, of light and darkness. 
But by means of this apparatus, the action of light is limited 
to a certain portion of the retina, which exactly represents 
by its form that of the luminous object. It is, then, an 
essential condition of vision, that the image should be 
formed upon the retina, and that the focus of the luminous 
rays should be bound upon this membrane. I ought also 
to add, that it has been proved by a curious experiment, 
for which we are indebted to Mariotte, that vision does 
not take place with equal distinctness when the image is 
formed upon different parts of the retina. If we place 
upon a horizontal black plane [as a sheet of black paper,] 
and on the same line three small white discs [wafers for 
example,] 5 or 6 centimetres [about 2 inches] apart, and 
look at them vertically, in such a position that the eye is 
distant from them 12 or 15 centimetres [about 5 or 6 
inches,] and that the nose of the observer is vertical to 
the middle disk,] then, by shutting one eye, and looking 
with the other at one of the lateral diiscs, the disc placed 
under the open eye ceases to be visible. This disc be- 
comes visible by varying the distance at which it was at 
first placed ; and when this has taken place, if we shut the 
eye which had previously been opened, and open that 
which had been closed, and fix it on the middle disc, we 
shall no longer see that which is verticle to it. The point 
of the retina an which is formed the image of the disc, 



LeCT. XX. ADAPTATION OF THE EYE. 369 

which becomes invisible, corresponds, in these different 
positions, to the base of the optic nerve. 

Maptation of the Eye to different Distances. — It is, then, 
clearly proved, that for vision to be perfectly distinct, our 
eye should be placed in such a manner that the image 
should be formed upon the sensible points of the retina, in 
the smallest possible dimensions, and with sufficient inten- 
sity. 

This being admitted, let us now see how these conditions 
can be constantly fulfilled, the distance at which we can see 
objects being variable. We perceive a star as distinctly as 
an object placed but a few centimetres off: all that is re- 
quired for the object to be distinctly seen is, that its size, 
and,, consequently, the intensity of its light, should increase 
in proportion to its distance. The image of a luminous 
object recedes further from, or advances nearer to, a lens, 
according as the body is brought nearer to, or is carried 
further away from, the opposite side of the lens. It is, 
therefore, certain, that the eye, by an act of volition, be- 
comes so modified as to see at different distances. In fact, 
if we look at a body, a black spot for instance, made upon 
a glass, placing it at different distances from the eye, we 
shall have a confused image of the objects more or less 
distant from the spot, whilst the latter will be very distinctly 
seen in every position, and however remote. With a 
healthy eye, vision is effected without either effort or fatigue 
at a distance of about 30 centimetres [= 11'8 inches,] but 
not for greater or less distances. This is the reason why it 
is no longer distinct after the eye has been looking at an 
object very near to it for several hours. 

In order to explain the property which this organ pos- 
sesses, of seeing objects placed at variable distances, w^e 
must adopt one or the other of the following two hypotheses: 
either we must assume that the retina communicates to the 
24 



370 VISION. Lect. XX. 

brain the distinct sensation of a luminous object, not only 
when its rays are collected into a single one, as when they 
reach it from a distance of about 30 centimetres [= 11*8 
inches,] but also when they are collected in a small, very 
hmited, circular space ; or we must suppose, that the cur- 
vature of the transparent cornea and of the crystalline lens, 
can be varied for different distances, and that the crystalline 
lens can change its position ; that is to say, augment or 
shorten its distance from the retina in diflferent cases. Ac- 
cording to the calculations of Olbers, it would be requisite, 
in order to have equally distinct vision at very different 
distances, namely, from 4 inches to an infinite distance, 
that the interval between the crystalline lens and the retina 
could vary at least ^th of an inch, supposing the convexity 
of the cornea and of the crystaUine lens to remain constant. 
The same result would be obtained, if we were to suppose 
that the convexity of the crystalline lens and the cornea 
varied, while the distance of the crystalline from the retina 
remained the same. Olbers also found, that vision would 
be distinct within the limits mentioned, if the radius of the 
cornea were capable of change, to the extent of about the 
^^^ths of an inch. 

An experiment made by Scheiner shows, that there are 
cases in which the image of an object appears to the same 
eye sometimes double, at others single. If, by means of a 
needle, we make in a piece of paper two holes, at a less 
distance from each other than the diameter of the pupil, 
and if we look through them with one eye only, at a certain 
distance the object will appear single ; but at a greater or 
less distance than this, it will appear double. If we close 
one of the holes, one of the two images will disappear. In 
the first instance, the two luminous fasciculi evidently meet 
upon the retina ; while, in the two other cases, the retina 
is more or less removed from their point of intersection. 



LeCT. XX. ADAPTATION OF THE EYE. 371 

By looking at the object directly, vision would be distinct 
at these different distances ; the eye, therefore, must undergo 
some modification in order to bring about this result. 

We ought, then, to be able to find in the intimate struc- 
ture of the eye, some peculiarities calculated to explain the 
faculty we possess of seeing distinctly at every distance. 
The different media of the eye have been long compared 
to an apparatus composed of lenses terminated by regular 
surfaces, and having all their axes on the same line repre- 
sented by the axes of the eye itself. On this hypothesis, 
all the luminous rays emanating from any point of an object 
ought to be concentrated at a single point called the focus ; 
and in order that the vision might be distinct, it w^ould be 
necessary that the retina should be so placed that the dif- 
ferent foci, corresponding to the different points of an ex- 
terior object, should be formed at its surface. But as the 
place at which the image is formed by refraction, approaches 
or recedes from the refracting apparatus, just as the object 
itself recedes from or approaches it, we ought to find in the 
structure of the eye some means of remedying this shifting of 
the image, by which the distinctness of the impression pro- 
duced upon the retina itself may be maintained. For this- 
purpose several hypotheses have been advanced. 

1st. It has been thought that the transparent cornea 
might vary its curvature so as to remedy this change of 
place of the image. But observation has proved that this 
curvature was invariable. 

2dly. Some physiologists fancied that the crystalline lens 
had the power of contracting, and that the curvatures of its 
two surfaces could change, so as to keep the image con- 
stantly upon the retina. Everything proves that this is pure 
hypothesis. 

3dly. Setting out from this fact, that the pupil dilates 
when the object recedes, and proportionately contracts as 



372 VISION. Lect. XX. 

the object approaches, natural philosophers have supposed 
that the vision of distant objects was effected by means of 
the rays traversing the less refracting marginal portion of 
the crystalline ; whilst the act of vision at short distances 
was performed exclusively by means of the rays passing 
through the more refracting layers of the centre of the crys- 
talline lens. In this manner the image would be always 
distinctly formed at the surface of the retina. It is needless 
to show here, that this explanation is at least very far from 
being complete. 

4thly. Some physiologists have had recourse to a change 
of place of the crystalline in the interior of the globe of the 
eye, in order to explain vision at every distance. But 
there is no evidence that such a movement of the lens is 
effected, and it is difficult to conceive the possibility of it. 

5thly. Finally, it has been thought that the contraction of 
the muscles of the eye, and the consequent pressure on this 
organ, were sufficient to lengthen or shorten its axis at will ; 
and, consequently, to change the position of the retina, and 
incessantly restore it to a suitable position for receiving the 
distinct image of the external object. This, also, is a pure 
hypothesis, which has nothing to support it. 

The distinctness of vision at every distance remained, 
then, inexplicable, and seemed to have escaped all the re- 
searches of physiologists and philosophers, when Sturm 
placed the question on its true ground, and clearly showed 
why all previous attempts to explain it had failed. 

According to Chossat's measurement of the eye of an ox, 
the anterior surface of the cornea is a segment of an ellip- 
soid of revolution about the major axis of the ellipse, which 
represents the horizontal section of this cornea; and the 
faces of the crystalline are segments of ellipsoids of revolu- 
tion about the lesser axes of their generating ellipses; the 
axes of these two ellipses not exactly coinciding in length. 



LeCT. XX. ADAPTATION OF THE EYE. 373 

Moreover, the axes of these three generating ellipses of the 
surfaces of the refracting media of the eye, coincide neither 
with the axis of the eye nor with each other. 

It follows, then, that in place of comparing the optical 
apparatus of the eye to a system of spherical lenses, whose 
axes were blended, we ought, according to Sturm, to con- 
sider the organ as " composed of several refracting media, 
separated by surfaces which are neither exactly spherical, 
nor even of revolution or symmetrical about a common 
axis." 

Sturm, studying the problem in all its generalities, has 
shown that, with a like composition of the eye, the fasci- 
culus of luminous rays, transmitted to the cornea by a 
point placed on the prolongation of the axis of the eye, 
could not be so refracted that all the rays could converge 
towards a single focus ; but the following is what hap- 
pens: — 

Fig. 33. 



Diagram Explanatory of Sturm's Hypothesis of Vision at different Distances. 

Let the circle aba^b' represent the aperture of the pupil^ 
and ox the axis of the eye : then suppose that a fasciculus 
of rays, parallel to the axis, falls upon the cornea. 

It will have there two planes, aoa' and bob', perpendi- 
cular to each other, so that all the luminous rays contained 
in the plane aoa', will converge towards the axis in one 
focus only, f, and all the rays contained in the plane bob', 
will be concentrated towards the axis in one point f. Let 
us call the distance ¥f, the focal interval. 



374 VISION. Lect. XX. 

At the point f draw a perpendicular, cc', at the axis, to 
the rays B/*and islf produced. At the pointy, also draw a 
perpendicular c d at the axis, to the extreme reflected rays 
AF and A^F. 

If, now, we consider a luminous ray of light traversing 
the pupil at any point m, situated beyond the planes aoa', 
bob', this ray will no longer meet the axis of the eye, but 
will be refracted so as to rest at the same time upon the 
line cfd and upon the line cfc'. Hence, it follows that; 

The luminous fasciculus which falls on the surface of the 
cornea parallel to the axis will be so refracted, that in the 
whole extent of the focal inter val,yF, it will form a very 
narrow and very concentrated fasciculus, surrounding the 
axis on all sides, and terminating very near it by a twisted 
surface {surface gauche.) 

It is within the focal interval, between the points/* and 
F, at the point r, for instance, that the retina is placed. 
Hence the refracted fasciculus depicts, on the surface of the 
retina, a very narrow elliptic surface around the axis, and 
on which all the rays which have traversed the opening of 
the pupil meet. 

It follows, then, that a luminous point, placed before the 
eye, does not meet upon the retina at a single point, but 
upon a very small surface, proceeding from the meeting of 
the retina and of the fasciculus concentrated about the axis 
in the focal interval yF. 

Let us suppose, now, that the exterior point recedes from 
or approaches the eye, the entire focal interval^F will at the 
same time change its place, so that the retina which at first 
was at R will be at r", or at r', being always contained be- 
tween the points f and f. Hence, it follows, that this re- 
tina will be always met by the concentrated fasciculus 
around the axis in the focal interval, and that the surface 
of intersection of this fasciculus, and of the nervous mem- 



LeCT. XX. LONG-SIGHTEDNESS. 375 

brane, will be very slightly modified, in order that the im- 
pression may not be sensibly altered, and that the percep- 
tion may preserve all its distinctness. 

That which we have said of an isolated luminous point, 
is applicable to each of the points of the illuminated ob- 
ject, placed before the eye ; and it is easy to understand 
how this new theory of the path of the luminous rays 
through the refracting media of this organ, accounts for 
such an important fact, and one which seemed difficult to 
explain, namely, that of the distinctness of vision at every 
distance. 

Long-sightedness. — Presbyt(2, or long-sighted persons, see 
objects distinctly at the distance of two or three feet. In 
their eyes the cornea is less convex than that in a perfect 
eye ; and, in fact, this defect of sight comes on with old 
age, and follows the general diminution of the secretions of 
all the tissues. By this flattening of the cornea, the focal 
interval of the rays, which emanate from the point of dis- 
tinct vision of the sound eye, is thrown behind the retina, 
and, therefore, long-sighted persons are under the necessity 
of increasing the distance of an object, in order that its 
image may be formed on this membrane. Those w^ho 
suffer from this defect, usually have the pupil but little 
dilated, as if a continual effort was made to use the cen- 
tre only of the crystalline lens, namely, the most refract- 
ing portion. To correct this defect, they are obliged to 
employ convex lenses, which diminish the divergence of 
the rays before they enter the eye. By this means the rays, 
emanating from an object placed at the point of ordinary 
vision, are bent by these lenses and brought into the di- 
rection they would have if the object were situated at the 
distance at which a long-sighted person saw distinctly. 

Short-sightedness.— The other defect of the eye, myopia, 
or short-sightedness, arises from an opposite cause ; namely, 



376 VISION. Lect. XX. 

a too great curvature of the transparent cornea. In this 
case, the rays proceeding from the point where ordinary 
vision occurs, form their focal interval in front of the re- 
tina ; and, hence, short-sighted persons employ diverging 
or concave eye-glasses. These lenses increase the diver- 
gence of the rays before they enter the eye ; and, in con- 
sequence, an object placed at the distance of normal vision, 
is seen under the divergence which it would have for a 
short-sighted person, if it "were brought near to the eye. 
Convergent and divergent meniscuses, or the periscopic 
lenses of Wollaston, correct these defects more effectually 
than ordinary lenses. The thickness of these meniscuses 
being necessarily less than that of the eye-glasses com- 
monly used, they absorb a smaller quantity of light, and 
the objects preserve more distinctness. 

Achromatism of the Eye. — The achromatism of the eye, 
which is perfect for objects situated at the distance of dis- 
tinct vision, is owing to the circumstance that the fascicu- 
lus which meets the retina, within the focal interval, being 
contracted around the axis, contains rays of every colour 
in a space too narrow for the coloured bands to be distinctly 
formed. 

We know, indeed, that if the spaces which separate 
images of different colours or intensity upon the retina are 
very small, these images cannot be separately perceived ; 
the sensation which w^e experience being the result of the 
simultaneous impression of neighbouring images. 

If, then, we cannot point out exactly the cause of the 
achromatism of the eye, we cannot, on the other hand, 
deny that there is in the structure of its lenticular appara- 
tus, that variety of curvatures, and of refractive and dis- 
persive power of the media, which are the general condi- 
tions observed in the structure of achromatic optical appa- 
ratus. 



LeCT. XX. CASE OF ERECT VISION. 377 

How do we appreciate the position, the distance, and the 
size, — in a word, the mode of existence of an object, and 
its relations to surrounding bodies ? What is the office of 
the two eyes ? 

What we have hitherto said, has been for the purpose 
of proving that the image of an object is formed upon the 
retina, and that it is distinct, but is inverted, as regards the 
object itself; and that this double effect is produced what- 
ever may be the distance between the object and the eye. 
Nevertheless, this image is not yet the sensation ; this only 
takes place when the modification experienced by the reti- 
na, has been transmitted to the seat of perception by means 
of the optic nerve. 

Cause of erect Vision. — But how does vision result from 
this modification made upon the retina by the rays which 
external objects transmit there ? The first question that 
presents itself to our notice, without occupying ourselves 
with the metaphysical part of the subject, is, that of the 
position of objects. It has been repeatedly said, by way 
of explaining the inversion of the images as regards the 
objects they represent, that we see the produced images 
in an inverted position. To see objects in the inverted 
position of their images, is what we call seeing objects 
erect. In appreciating the position of bodies and their 
erection, we merely compare the position of their different 
parts with that of surrounding bodies. Without this, the 
words reversed and erected as applied to objects, would be 
devoid of all meaning. To us, a man is in the upright 
position when his feet are towards the earth, and his head 
in the part most distant from it ; and the reversed image 
which he forms upon the retina, in no way deranges the 
respective position of the various parts of the man in re- 
rard to the earth. In the image, the feet are equally nearer 



378 VISION. Lect. XX. 

the earth than the head. If an object presents itself to 
us really reversed, relatively to the position in which we 
are accustomed to see it, we consider that it has acquired 
the reversed position because its image upon the retina is 
equally so, by comparison, with that which we ourselves 
hold, and to that in which we usually see it. We know that 
a man, and that each of us, has his, or our feet upon the 
ground : but when we see in the image formed upon the 
retina by a dancer, that his head touches the ground, we 
know that we see it in a reversed position. 

Judgment of Distance mid Size. — We judge of the dis- 
tance and magnitude of objects in many ways : if they 
were placed constantly at one distance, and always equally 
illuminated, we should be able to measure their size by 
that of the image painted on the retina. The dimension 
of this image is, in general, proportional to the visual an- 
gle made by two right lines drawn from the extremities of 
the object to the centre of the retina : this we call the appa- 
rent size. In judging of the distance of objects, we have 
perception, 1st, of the movements which the eye makes in 
order that the luminous cone, which the object sends to 
the pupil, and which is more or less divergent according 
to the distance, may form its focus upon the retina ; 2dly. 
Of the movements by which we bring the optic axes of the 
two eyes more or less near one another, in order to make 
them converge upon an object placed at different distances. 
But this latter means of appreciating distances can no longer 
serve us when the bodies are at great distances, for then 
the two axes become almost parallel, and we are subject 
to optical illusions. Thus, the two rows of trees of a 
long avenue appear to approach nearer to each other in 
proportion as they are further off; and the lateral walls of 
a long gallery, also, present this appearance. 



LeCT. XX. SINGLE VISION. 379 

The intensity of the light which we receive from an 
object, and which we know diminishes with the distance, 
assists us also in judging of the distance; but such a judg- 
ment is rendered uncertain by atmospheric variations, which 
continually modify the quantity of light received by the 
object. Lastly, in forming an opinion respecting the real 
magnitude of objects which are more or less distant from us, 
we depend partly on our estimate of their distance, and 
partly on their apparent magnitude, which is measured by 
the size of the images produced on the retina. The errors 
that we frequently commit when estimating distance, are 
one source of the illusions in judging of real magnitude: 
these are most frequently made in the dark, as in the phan- 
tasmagoria. 

Single Vision. — What is the use of the two eyes in the 
act of vision? Whilst the object is situated very far from 
us, the images formed in the two eyes are identical, and 
vision is effected as with one eye, the optical axes being 
then sensibly parallel. The single impression produced by 
a body seen with two eyes is, in this case, the result of an 
intellectual act, which, from custom, we execute with an 
inconceivable rapidity. We do not perceive two objects, 
although the image be double, because experience has 
taught us that this object is single in every case where two 
identical representations are produced upon two parts of 
the retina, which are necessarily correspondent, in order 
that vision may be distinct. It is the same with the organ 
of touch. If we place all the fingers of one hand on a ball, 
we do not experience the sensation of five balls, but only 
of one. If we look at a body with two eyes, and then 
compress the globe of one of them so as to change the posi- 
tion of the image on the retina, and alter the axis of one of 
the two eyes, the body instantly appears double. This is 



380 VISION. Lect. XX, 

the cause of strabismus or squinting. An analogous phe- 
nomenon is also produced with the sense of touch. To 
effect this, cross the fore and middle finger of one hand, 
and with their extremities touch a ball : you will experience 
an illusion, and fancy that you touch two different balls in- 
stead of one. 

Wollaston supposed that the unity of vision was attribu- 
table to an anatomical cause. This philosopher thought 
that the two optic nerves, at the point where they unite, in 
passing out from the brain, and afterwards separate and 
proceed to the eyes, divide in such a way that each nerve 
forms half of both retinse. From this semi-decussation of 
the optic nerves, it happens that the right side of both 
retinae is formed by the division of one nerve, and the left 
side, by the division of the other nerve; so that all images 
of objects out of the optic axis, are perceived by one and 
the same nerve in both eyes, and the two excited nerves, 
consequently, furnish a single and complete image. By 
this anatomical arrangement would be explained the phe- 
nomenon which Wollaston and Arago observed in their 
own persons, after long study, namely, that of seeing only 
half of every object. We must, however, admit, that at 
first, anatomical observations did not confirm this opinion ; 
and that we may also oppose to it the fact of the single 
sensation of sound by the two ears, by means of the two 
acoustic nerves, which are perfectly distinct from each other 
in their passage to the brain. 

Identical images painted upon the retina of two eyes by 
a distant object, are such that there is no difference between 
the perception produced by solid bodies in sculpture, or in 
relief, and a draw^ing made on a flat surface, in which the 
rules of perspective are followed. A picture representing 
objects which we are accustomed to see at a certain dis- 



LeCT. XX. THE STEREOSCOPE. 381 

tance, if it be properly illuminated in its different parts, 
gives us the perfect image of the original, so that the illu- 
sion is complete ; of this we have an example in the diorama. 
But this is no longer the case when the object is at a very 
short distance from the eye. We are indebted to Wheat- 
stone for a series of extremely ingenious experiments upon 
this subject. When a solid body, a cube for instance, is 
very near the eyes, its projection on the retina of each eye 
forms there two different images ; they resemble each other 
so slightly, that if we supposed them drawn, we could 
scarcely, by looking at them, recognise that they belonged 
to the same body. Notwithstanding this difference, we see 
a single object: we must then conclude, from these facts, 
that the perception in relief may be produced by the simul- 
taneous impression of two images formed in each eye ; in 
other words, to see objects as they are, becomes an illusion. 
Notwithstanding the observations of Wheatstone, we must, 
however, assume, that a single eye is capable of estimating 
the solidity of bodies, as is seen daily in persons who have 
lost one. Experience, custom, and the other senses, assist 
in correcting this defect. 

The Stereoscope. — By looking at the same lime at the 
images of two drawings, obtained by copying the two pro- 
jections of a solid body upon the retinae of the two eyes, 
Wheatstone succeeded in producing the same sensation as 
that which would have been produced by the solid body. 
When the observation is made in such a way that the images 
of the two drawings are formed in the same manner, and 
upon the same points of the retina which the two projections 
of the solid occupy, the illusion is complete, and it is im- 
possible to believe that we have before the eyes only paint- 
ings made upon a plane. 



Lect. XX. 




Front View of Wheatstone's Stereoscope. 

A A'. Two plain mirrors, whose backs form an angle of 90° with each other. 

B. Upright, against which the common edge of the mirrors is fixed. 
C C Two drawings which slide in grooves made in the pannels D D'. 
The observer must place his eyes as near as possible to the mirrors, the right eye 
before the right hand mirror, and the left eye before the left-hand mirror. 




Plan of Wheatstone's Sterescope. 
(The letters refer to the same object as in the preceding figure.) 

Wheatstone has given the name of stereoscope to the 
instrument by the aid of which this illusion is produced. 



LeCT. XX. DURATION OF IMPRESSIONS. 

Fig. 36. 



383 



r~Ni 




a a' . Outline fissures placed in the Stereoscope: a being seen by the left ej'e, and a' 
by the right eye. 
b. Outline of the fi^'iire seen in the Stereoscope hy the simultaneous perception 
of the figures a a' . 

It consists of two inclined mirrors, upon which are 
formed by reflection the images of the two paintings repre- 
senting the projections of a solid body in both eyes. The 
two images are observed by applying the eyes to two 
openings which allow the two images formed on the mirrors 
to be seen. 

Duration of Impressions. — Among the most curious phe- 
nomena of vision, is that of the continuance of impressions 
received on the retina. Observe a burning coal when being 
whirled round : if the rotation be sufficiently rapid, you 
fancy you see a circle of fire. It is evident that this illu- 
sion can only be explained by assuming that the sensation 
produced by the luminous body remains for a certain time, 
which can be estimated by the interval necessary for the 
coal, in revolving, to return again to the same point; so 
that we see it simultaneously at all the points which it suc- 
cessively traverses. The apparent augmentation of volume 
which a cord undergoes during vibration, — the disappear- 
ance of the spokes of a wheel which revolves with great 
rapidity, — the luminous train of shooting stars, — and the 
white appearance of a revolving disc, on which the seven 
colours of the spectrum are painted, are phenomena depend- 
ing on the same cause; that is, the duration of impressions 
on the retina. If light were instantaneous all these phe- 
nomena would cease. Look steadfastly for some seconds 



384 VISION. Lect. XX. 

at any luminous body, close the eyes and you will still 
see it. 

In order to ascertain the length of this duration, Aime 
contrived to revolve, in opposite directions, two discs 
fixed on one axis. One of them was perforated with a 
great number of holes, in the form of equal and symmetri- 
cally disposed sectors; the other had but one such hole. 
When a fasciculus of light was made to fall on this appa- 
ratus while in motion, in a dark place, the eye which looks 
along the common axis of the two discs, perceive some- 
times one illuminated sector, whose position is variable and 
dependent on the coincidence of the single aperture of the 
second disc with each of those of the first ; sometimes two, 
sometimes three, or even more, and, lastly, one disc of light. 

These different impressions depend on the rapidity of 
rotation. There is only one sector if the velocity of motion 
be such, that the second coincidence takes place when the 
impression made upon the retina by the first has ceased. 
There are two sectors if the impression continues until the 
second coincidence takes place, and so on. It thus becomes 
easy by this apparatus, to determine the duration of the 
impressions upon the retina. Some very ingenious appa- 
ratus, which likewise serves to amuse children, have been 
constructed on the same principle as that of Aime's instru- 
ment just described. Around a circle is placed a number 
of figures of men, exactly alike in dress and shape, and all 
represented in motion. They are arranged successively, 
one after the other, each representing a different but suc- 
cessive position of a given exercise, as, for example, 
sawing, playing the violin, dancing, &c. The first circle 
is seen through the slits of a second one. By turning both 
upon one axis, the eye receives the impression of each of 
the positions of the figure, at the moment of the passage of 
the corresponding opening, and preserves the impression 



LeCT. XX. OCULAR SPECTRA. 385 

of the preceding until the following one takes place. Thei-e 
results from this persistence, an effect similar to that which 
would be produced by the object in motion. 

Plateau, who long studied this subject, discovered that, 
in order to produce a complete impression, the light ought 
to act for a certain time; that the total duration of the im- 
pression is the same for all the colours, and may be ap- 
proximatively estimated at 0'''34; that the interval of time, 
during which the impression preserves the same intensity, 
is as much more considerable as the light is more mode- 
rated ; that it is different for rays of different colours ; for 
instance, it is longer for the blue than for the red and white 
light ; and that, in fact, the total duration of the impressions 
is so much the more persistent as the light is the more in- 
tense and its action less prolonged. A cannon-ball does 
not leave the impression of its passage like a shooting star, 
because the intensity of its light is less. 

Ocular Spectra, — Besides the persistence of impression 
received by the retina, other phenomena occur to us by no 
means less curious, when we have an object fixed for a cer^ 
tain time. Look at a disc of any colour placed in the mid- 
dle of a piece of black card, after having fixed your eyes on 
it for a certain time remove them rapidly to a white ground, 
or cover them with a cloth, and you will then apparently 
see a disc, in form similar to the first, but having a colour 
complementary to it. Thus, if the disc be red, the image 
will be green ; if yellow, it will appear violet ; and if white, 
it will look gray. These apparent sensations have received 
the name of accidental colours. Plateau seems to have de- 
monstrated that these images cease, after having presented 
a singular series of phenomena ; thus it appeared, that after 
a certain time they vanish, and give place to an image 
which has really the colour of the object ; this second dis- 
appears, and that of the complementary colour returns. 
24 



386 VISION. Lect. XX. 

These images become weaker after having undergone this 
series of alternations. 

Accidental colours form, with each other, combinationslike 
real ones. The following fact puts this curious observation 
beyond a doubt: — place upon a black ground two squares of 
paper, one violet, for example, the other orange, both having 
black points in their centres. Carry the eyes alternately 
from one point to the other, and after each passage shut 
the eyes, and you will fancy you see three squares : one 
yellow, which is complementary to violet; one blue, com- 
plementary to the orange; and a third, between the two 
others, of a green colour, which is the precise shade formed 
by the yellow and blue. In this experiment the primitive 
impressions upon the retina, are only the superposition of 
the two partial impressions which they would manifest if 
we had observed only one black point ; but as the direc- 
tion of the optic axes differs according as we look at one or 
the other of these points, it follows that the points of the 
retina which receive these two partial impressions are not 
symmetrical. From the juxtaposition of the two squares it 
results, that the accidental image of the orange colour for 
the first partial impression, is superposed on that of the 
violet for the second. The intermediate square, which we 
perceive when closing the eyes, is owing to this superposi- 
tion ; consequently, we must conclude that the accidental 
yellow and blue form the green, as real blue and yellow 
would do. We should arrive at the same conclusion 
"whatever were the colours of the two squares. Yet we 
observe a difference when they are tinted with complemen- 
tary colours ; in this case the intermediate square, arising 
from the superposition of the accidental images, is black, 
and not white, as takes place in the mixture of two real 
colours. 

Accidental colours combine with real ones exactly as the 
latter would do with each other. To be convinced of this 



LeCT. XX. OCULAR SPECTRA. 387 

we need only observe an image accidentally coloured, not 
upon a white cardboard but on a coloured one; the image 
has no longer the complementary colour, but that which 
results from the mixture of this colour with that of the 
cardboard on which it is tixed. 

Finally, I am anxious to say a few words on the acci- 
dental colours formed around objects at the same instant at 
which we fix them. If we look for a certain time at a co- 
loured object, placed in the middle of a white cardboard, 
we see upon the edges a fringe of complementary colour. 
Observe a strip of white paper pasted on a coloured leaf, 
and place it near a window, in order that it may receive the 
greatest possible amount of light ; the strip will soon appear 
to have acquired the complementary colour to that of the 
leaf. All white bodies, when powerfully illuminated, seem 
to be larger than black objects, although in reality their di- 
mensions are the same. This experiment succeeds as w'ell 
if we employ two similar discs, the one black, placed upon 
a white ground, the other w'hite on a black ground, the 
latter appears to be larger than the other. All these facts 
evidently prove, that each impression produced upon the 
retina is accompanied by an accidental fringe, so that the 
excitation is extended beyond the points of the retina, where 
the image is formed. 

Important applications of these principles are made in the 
arts in which coloured objects are employed. If the colours 
which are neighbouring ones, and which mutually influence 
each other, are complementary, there follows from their re- 
ciprocal action a greater brilliancy ; the black and the white 
become, the one more brilliant, the other more deep. On 
the contrary, all those which are near each other in the 
series of the seven colours, weaken and injure each other 
when placed side by side. Pictures, carpets, tinted papers, 
and decorations in general, sometinjes present bad effects, 
when the reciprocal influences of neighbouring colours have 



388 VISION. Lect. XX. 

not been attended to in their construction. We are in- 
debted to M. Chevreul for a work on this subject, which is 
remarkable and complete. 

I cannot pass silently over the ingenious theory by means 
of which Plateau has attempted to explain all the phenomena 
now alluded to. According to him, when the retina has 
been impressed and agitated by light, emanating from an 
object, and the cause of the excitation has ceased, the 
retina returns to its normal position, after a series of de- 
creasing oscillations. The conditions through which it 
successively passes during the continuation of these oscil- 
lations, produce opposed sensations. There is opposition 
between the black and the white, and in general between 
the effects produced by two complementary colours. In 
fact, two accidental complementary colours produce, by 
their superposition, black ; that is to say, no effect. During 
the continuation of the excitation of the retina, the points of 
the latter, which are near to those upon which the image is 
formed, likewise suffer oscillations ; which, being identical 
with those produced upon a tense membrane, ought to be 
in a direction opposed to the first, just as we know the 
vibrations of two neighbouring concamerations [arches] of 
a vibrating plate are in an opposite direction. There is, 
then, a neighbouring fringe which produces the effect of a 
complementary colour, or that of an opposite condition. 

In a word, a portion of the retina being disturbed from 
its normal state, and the cause of the disturbance having 
ceased, it returns to a state of repose by a series of 
oscillations, which vary in their directions and in their in- 
tensity with the time. The movement communicated to 
it is propagated to all the neighbouring parts by a series 
of oscillations, which also vary in intensity and direction^ 
according to their distance from the place of the direct im*- 
pression. 

THE END. 



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A» ATL^S OF ^•mCimi^T ©BOGaiiPHir, 
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Late Lord Bishop of Litchfield, 

CONTAINING TWENTY-ONE COLOURED MAPS, AND A COMPLETE ACCENTUATED INDEX. 

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BUTLER'S AN CIENT GEOGRAPHY. 

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FROM THE EARLIEST TIMES TO THE TREATY OF VIENNA ; TO WHICH [S ADDED, A 

SUMMARY OF THE LEADING EVENTS SINCE THAT PERIOD, FOR THE 

USE OF SCHOOLS AND PRIVATE STUDENTS. 

BY H. -WHITE, B.A., 

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Messrs. Lea ^ Blanchard : 

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KISTOH-^ OP THE TLTiTOHWiATlON IN GTlRm.A.NTr. 

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Author of the " Principles of Practical Gardening-," " The Gardener's Almanac," &c. 

WITH ONE HUNDRED AND EIGHTY WOOD-COTS. 

EDITED, WITH NUMEROUS ADDITIONS, BY DAVID LANDRETH, OF PHILADELPHIA. 

In one large royal duodecimo volume, extra cloth, of nearly Six Hundred and Fifty 
double columned Pages. 
This edition has been pjeatly altered from the original. Many articles of little interest to Ameri- 
cans have been curtailed or wholly omitted, and much new matter, with numerous illustrations, 
added, especially with respect to the varieties of fruit which experience has shown to be peculiarly 
adapted to our climate. Still, the editor admits that he has only follov^'ed in the path so admirably 
marked out by Mr. Johnson, to whom the chief merit of the work belongs, it has been an object 
with the editor and publishers to increase its popular character, thereby adapting it to the larger 
class of horticultural readers in this country, and they trust it wiU prove what they have desired it 
to he, an Encyclopaedia of Gardening, if not of Rural Affairs, so condensed and at such a price as to 
be within reach of nearly all whom those subjects interest. 

" This is a useful compendium of all that description of information which is valuable to the 
modem gardener. It quotes largely from the best standard authors, journals, and transactions of 
societies; and the labours of the American editor have fitted it for the United States, by judicious 
additions and omissions. The volume is abundantly illustrated with figures in the text, embracing 
a judicious selection of those varieties of fruits which experience has shown to be well smted to the 
United States. — SiUiman's Journal. 

" This is the most valuable work we have ever seen on the subject of gardening ; and no man of 
taste who can devote even a quarter of an acre to horticulture ought to be without it. Indeed la- 
dies who merely cultivate flowers within-doors, will find this book an excellent and convenient 
counsellor. It contains one hundred and eighty wood-cut illustrations, which give a distinct idea 
of the fruits and garden-arrangements they are intended to represent. 

" Johnson's Dictionary of Gardening, edited by Landreth, is handsomely printed, well-bound, and 
sold at a price which puts it within the reach of all who would be likely to buy it." — Evergreen. 

THE COM PLETE FLORIST. 
A iHL£Li!nj£LiM or G.a.RBszrixa'G, 

CONTAINING PRACTICAL INSTRUCTION FOR THE MANAGEMENT OF GREENHOUSE 

PLANTS, AND FOR THE CULTIVATION OF THE SHRUBBERY— THE FLOWER 

GARDEN, AND THE LAWN— WITH DESCRIPTIONS OF THOSE PLANTS 

AND TREES MOST WORTH V OF CULTURE IN EACH 

DEPARTMENT. 

■WITH ADDITIONS AND AlVI EN D jM E N T S, 

ADAPTED TO THE CLIMATE OF THE UNITED STATES. 

In one small volume. Price only Twenty-five Cents. 

THE COMPLETE KITC HEN A ND FRUIT GARDENER. 

A SELECT MANUAL OF KITCHEN GARDENING, 

AND THE CULTURE OP FRUITS, 

CONTAINING FAMILIAR DIRECTIONS FOR THE MOST APPROVED PRACTICE IN EACH 

DEPARTMENT. DESCRIPTIONS OF MANY VALUABLE FRUITS, AND A 

CALENDAR OF WORK TO BE PERFORMED EACH 

MONTH IN THE YEAR. 

THE WHOLE ADAPTED TO THE CLIMATE OF THE UNITED STATES. 

In one smaU volume, paper. Price only Twenty-five Cents. 

LANDRETH»S RURAL REGISTER AND ALE^ANAO, FOR 1848, 

WITH NUMEROUS ILLUSTRATIONS. 



STILL ON HAND, 
A PE-W COPIES or THE RECflSTER FOR 1847, 

WITH OVER ONE HUNDRED WOOD-CUTS. 

This work has 150 large 12mo. pages, double columns. Though published annually, and contain- 
ing an almanac, the principal part of the matter is of permanent utility to the horticulturist and 
fariner. 



LEA AND BLANCHARD'S PUBLICATIONS. 

LAW BOOKS. 
HILLIARD ON REAL ESTATE. 

NOW READY. 



THE AMSEIOAH X.AW OF REAIa PROPERTY. 

SECOND EDITION, REVISED, CORRECTED, AND ENLARGED. 

BY FRANCIS HILLIARD, 

COUNSELLOR AT LAW. 

In two large octavo volumes, beautifully printed, and bound in best law sheep. 

This book is designed as a substitute for Cruisers Digest, occupying the 
t,ame ground in American law which that work has long covered in the 
linglish law. It embraces all that portion of the English Law of Real 
Estate which has any applicability in this country ; and at the same time it 
embodies the statutory provisions and adjudged cases of all the States upon 
the same subject ; thereby constituting a complete elementary treatise for 
American students and practitioners. The plan of the work is such as to 
render it equally valuable in all the States, embracing, as it does, the pecu- 
liar modifications of the law alike in Massachusetts and Missouri, New 
York and Mississippi. In this edition, the statutes and decisions subse- 
quent to the former one, which are very numerous, have all been incorpo- 
rated, thus making it one-third larger than the original work, and bringing 
the view of the law upon the subject treated quite down to the present time. 
The book is recommended in the highest terms by distinguished jurists of 
different States, as will be seen by the subjoined extracts. 

" The work before us supplies this deficiency in a highly satisfactory manner. It is beyond all 
question the best work of the kind that we now have, and although we doubt whether this or any 
other work wiU be Ukely to supplant Cruise's Digest, we do not hesitate to say, that of the two, 
this is the more valuable lo the American lawyer. We congratulate the author upon the success- 
ful accomplishment of the arduous task he undertook, in reducing the vast body of the American 
Law of Real Property to ' portable size,' and we do not doubt that Ms labours will be duly appre- 
ciated by the profession." — Law Reporter, Aug., 1846. 

Judge Story says : — "I think the work a very valuable addition to our present stock of juridical 
literature. It embraces all that part of Mr. Cruise's Digest which is most useful to American law- 
yers. B-ut its higher value is, that it presents in a concise, but dear and exact form, the substance 
of American Law on the same subject. 1 know no work thit we possess, whose practical utility is 
likely to he so extensively felt." " The wonder is, that the autlior has been able to bring so great a 
mass into so condensed a text, at once comprehensive and lucid." 

Chancellor Kent says of the work (Conxmentaiies, vol. iL, p. 635, note, 5th edition) :— " It is a work 
of great labour and intrinsic value." 

Hon. Rufus Choate savs :— " Mr. Hilliard's work has been for three or four years in use, and 1 
think that Mr. Justice Story and Chancellor Kent express the general opinion of the Massachusetts 
Bar." 

Professor Greenieaf says : — " 1 had already found the first edition a veiy convenient book of refe- 
rence, and do not doubt, from the appearance of the second, that it is greatly improved." 

Professor J. H. Townsend, of Yale College, says :— 

" I have been acquainted for several years with the first edition of Mr. HilUard's Treatise, and 
have fonned a very favourable opinion of it. 1 have no doubt the second edition wiU. be found even 
more valuable than the first, and I shall be happy to recommend it as I may have opportunity. I 
know of no other work on the subject of Real Estate, so comprehensive and so well adapted to the 
itate of the law in this country." 



LEA AND BLANCHARD'S PUBLICATIONS. 



LAW BOOKS, 



ADDISOr^ ON CONTRACTS, 



BY C. G. ADDISON, ESQ., 

Of the Inner Temple, Barrister at Law. 
In one volume, octavo, handsomely bound in law sheep. 

In this treatise upon the most constantly and frequently administered 
branch of law, the author has collected, arranged and developed in an intel- 
ligible and popular form, the rules and principles of the Law of Contracts, 
and has supported, illustrated or exemplified them by references to nearly 
four thousand adjudged cases. It comprises the Rights and Liabilities of 
Seller and Purchaser ; Landlord and Tenant ; Letter and Hirer of Chattels ; 
Borrower and Lender ; Workman and Employer ; Master, Servant and Ap- 
prentice ; Principal, Agent and Surety; Husband and Wife; Partners; 
Joint Stock Companies ; Corporations ; Trustees ; Provisional Committee- 
men ; Shipowners; Shipmasters; Innkeepers; Carriers; Infants; Luna- 
tics, &c. 

WHEATON'S INTERNATIONAL LAW. 



BI.EME2^TS or I3MTEB.I7 ATIOS^-AL l^AySff-. 

BY HENRY WHEATON, LL. D., 

Minister of the United States at the Court of Russia, &c. 

THIRD EDITION, REVISED AND CORRECTED. 

In one large and beautiful octavo volume of 650 pages, extra cloth, or fine law sheep. 

" Mr. Wheaton's work Ls indispensable to every diplomatist, statesman and lawyer, and necessary 
indeed to all public men. To every philosophic and liberal mind, the study must be an attractive 
and in the liands of our author it is a delightful one."— North American. 



HILL ON TRUSTEES. 



A PRACTICAL TREATISE ON THE LAW RELATING TO TRUSTEES, 

THEIR POWERS, DUTIES, PRIVILEGES A^D LIABILITIES. 

BY JAMES HILL, ESQ., 

Of the Inner Temple, Barrister at Law. 

EDITED BY FRANCIS J. TROUBAT, 

Of the Philadelphia Bar. 

In one large octavo volume, best law sheep, raised bands. 

<' The editor begs leave to iterate the observation made by the author that the work is intended 
principally for the instruction and guidance of tiTistees. That single feature very much enhanceig 
its practical value." 

ON THE PRINCIPLES OF CRIMINAL LAW. 

Iq one 18mo. volume, paper, price 25 cents. 
BEING PART 10, OF "SMALL BOOKS ON GREAT SUBJECTS." 



LEA AND BLANCHARD'S PUBLICATIONS. 

LAW BOOKS. 

THE EQUITABLE JURISDICTION OF THE COURT OF CHANCERl 

COMPRISING 

ITS RISE, PROGRESS AND FINAL ESTABLISHMENT. 

TO WHICH IS PREFIXED, WITH A VIEW TO THE ELUCIDATION OF THE MAIN SUB- 
JECT, A CONCISE ACCOUNT OF THE LEADING DOCTRINES OF THE COMMON 
LAW, AND OF THE COURSE OF PROCEDURE IN THE COURTS OF COM- 
MON LAW, WITH REGARD TO CIVIL RIGHTS; WITH AN ATTEMPT 
TO I'RACE THEM TO THEIR SOURCES ; AND IN WHICH 
THE VARIOUS ALTERATIONS MADE BY THE 
LEGISLATURE DOWN TO THE PRESENT 
DAY ARE NOTICED. 

BY GEOHGE SPSHOE, ESQ., 

One of her Majesty's CounseL 

IN TWO OCTAVO VOLUMES. 

Volume I., embracing the Principles, is now ready. Volume II. is rapidly preparing and will 
api)ear eai'ly in 1848. It is based upon the work of Mr. JMaddoclc, brought down to tlie present 
time, and embracmg so much of the piactice as counsel are called on to advise upon. 

CONTAINING EXPLANATIONS OF SUCH TECHNICAL TERMS AND PHRASES AS OCCUP 

IN THE WORKS OF LEGAL AUTHORS, IN I'HE PRACTICE OF THE COURTS, 

AND IN THE PARLIAMENTARY PROCEEDINGS OF THE HOUSE OF LORDS 

AND COMMONS, TO WHICH IS ADDED, AN OUTLINE OF AN 

ACTION AT LAW AND OF A SUIT IN EQUITY. 

BY HENRY JAMES HOLTHOUSE, ESQ., 

Of the Imier Temple, Special Pleader. 
EDITED FROM THE SECOND AND ENLARGED LONDON EDITION, 

WITH NUMEROUS ADDITIONS, 
BY HENRY PBNINGTON, 

Of the Pluladelphia Bar. 

In one large volume, ro3'al 12mo., of about 500 pages, double columns, handsomely 

bound in law sheep. 

" This is a considerable improvement upon the former editions, being bound with the usual law 
binding, and tiie general execution admirable — the paper excellent, and the printing clear and 
beautiful. Its peculiar usefulness, however, consists in the'valuable additions above referred to, 
being intelligible and well devised defiuitions of such phrases and technicalities as are pecuhar to 
the practice in the Courts of this country. — While, therefore, we recommend it especially to the 
students of law, as a safe guide through the intricacies of their study, it will nevertheless be found 
a valuable acquisition to the library of the practitioner liimself." — Alex. Gazette. 

" This work is intended rather for the general student, than as a substitute for many abridgments, 
digests, and dictionaries in use by the pi-ofessional man. Its object principally is to impi'ess accu- 
rately and distinctly upon the mind the meaning of the technical terms of the law, and as such 
can hardly fail to be generally uscfuL There is much curious information to be found in it in re- 
gard to the peculiarities of the ancient Saxon law. The additions of the American edition give 
increased value to the work, and evince mucli accuracy and cdLre,"—Femisylvania Law Journal. 

A PRACTICAL TREATISE ON MEDICAL JURISFRUDENCE. 

BY ALFRED S. TAYLOR, 
Lecturer on Medical Jurisprudence and Chemistry at Guy's Hospital, London. 

With numerous Notes and Additions, and References to American Law, 

BY R. E. GRIFFITH, M.D. 
In one volume, octavo, neat law sheep. 

TAYLOR'S 'M.M.l^-U^LT, OF T©XIG0i:i.OG-"Sr. 
IN ONE NEAT OCTAVO VOLUME. 

A NEW WOEK, NOW KE.i.DY. 

OUTLINES OF A COURSE OF LECTURES ON MEDICAL JURISPRUDENCE. 

IN ONE SMALL OCTAVO VOLUME. 



LEA AND BLANCHARD'S PUBLICATIONS. 



LAW BOOKS. 



E A S T'S REPORTS. 



REPOHTS OF GASHS 

ADJUDGED AND DETERMINED IN THE COURT 
OF KING'S BENCH. 

WITH TABLES OF THE NAMES OF THE CASES AND PRESTCIPAL MATTERS. 

BY ED-WARD HYDE EAST, ESQ., 

Of the Inner Temple, Barrister at Law. 

EDITED, WITH KOTES AND REFERENCES, 

BY G. M. WHARTOTf, ESQ., 

Of the Philadelphia Bar. 

En eight large royal octavo volumes, bound in best law sheep, raised bands and double 
titles. Price, to subscribers, only twenty-five dollars. 

In this edition of East, the sixteen volumes of the former edition have 
been compressed into eight — two volumes in one throughout — but nothing 
has been omitted ; the entire work will be found, with the notes of Mr. 
Wharton added to those of Mr. Day. The great reduction of price, (from 
$72, the price of the last edition, to $25, the subscription price of this,) 
together with the improvement in appearance, will, it is trusted, procure for 
it a ready sale. 

A NEW WORK ON COURTS-MARTIAL. 



A TREATISE ON AMERICAN MILITARY LAW, 

AND THE 

PRACTICE OF COURTS-MARTIAL, 

WITH SUGGESTIONS FOR THEIR EMPROVEMENT. 
BY JOHN O'BRIEN, 

.LIEUTENANT UNITED STATES AKTILLERY. 

In one octavo volume, extra cloth, or law sheep. 
"This work stamls relatively to Amei-ican Military Law in the same position that Blackstone's 
Commentaries stand to Common Law." — U. S. Gazette. 

CAMPBELL'S LORD CHANCELLORS. 



LIVES OF THE LORD CHANCELLORS AND KEEPERS OF 
THE GREAT SEAL OF ENGLAND, 

FROM THE EARLIEST TIMES TO THE REIGN OF KIN& GEORGE IV., 

BY JOHN LORD CAMPBELL, A.M., F.R.S.E. 

FIRST SERIES, 

In three neat demy octavo volumes, extra cloth, 

BRINGING THE WORK TO THE TIME OF JAMES II., JUST ISSUED. 

PREPARING, 

SECOND SERIE S, 

In four volumes, to match, 

CONTAINING FROM JAMES II. TO GEORGE IV. 



LEA AND BLANCHARD'S PUBLICATIONS. 

YOUATT AND SKINNER'S 

STANDARD WORK ON THE HORSE. 



THE HORSE. 

BY WILLIAM YOUATT. 

A NEW EDITION, WITH NUMEROUS ILLUSTRATIONS. 

TOGETHER WITH A 

GEHXSEAI. HISTORir OF THE HORSS; 

A DISSERTATION ON 

THE AMERICAN TROTTING HORSE; 

HOW TRAINED AND JOCKEYED. 

AN ACCOUNT OF HIS REMARKABLE PERFORMANCES; 

AND 

AN USSR'S* ON TlXi: ASB ANH THS Z^XTZiZ!, 

BY J. S. SKINNER, 

Assistant Post-Master-General, and Editor of the Turf Register. 

This edition of Youatt's well-known and standard work on the Manage- 
ment, Diseases, and Treatment of the Horse, has already obtained such a 
wide circulation throughout the country, that the Publishers need say no- 
thing to attract to it the attention and confidence of all who keep Horses or 
are interested in their improvement, 

" In introducing this very neat edition of Youatt's welI-kno%vn book, on ' The Horse,' to our 
readers, it is not necessary, even if we had time, to say anything to convince them of its worth ; it 
has been highly spoken of, by those most capable of appreciating its merits, and its appearance 
under the pati-onage of the 'Society for the Diffusion of Useful Knowledge,' with Lord Brougham 
at its head, affords a full guaranty for its high character. The book is a very valuable one, and we 
endorse the recommendation of the editor, that every man who owns the ' hair of a horse,' should 
have it at liis elbow, to be consulted like a family physician, ' for mitigating the disorders, and pro- 
longing the life of the most interesting and useful of all domestic animals.' " — Farmer's Cabinet. 

" This celebrated work has been completely revised, and much of it almost entirely re-written 
by its able author, who, from bemg a practical veterinaiy surgeon, and withal a great lover and 
excellent judge of the animal, is pai-ticularly well qualified to write the history of the noblest of 
quadrupeds. Messrs. Lea and Blanchard of Philadelphia have republished the above work, omitting 
a few of the first pages, and have supplied their place with matter quite as valuable, and perhaps 
more interesting to the reader in this country ; it being nearly 100 pages of a general history of the 
horse, a dissertation on the American trotting horse, how trained and jockeyed, an account of his 
remarkable performances, and an essay on the Ass and Mule, by J. S. Skinner, Esq., Assistant Post- 
jiaster-General, and late editor of the Turf Register and American Farmer. Mr. Skinner is one 
of our most pleasing writers, and has been familiar with the subject of the horse from childhood, 
and we need not add that he has acquitted himself well of the task. He also takes up the import- 
ant subject, to the American breeder, of the Ass, and the Mule. This he treats at length and con 
amore. The Philadelphia edition of the Horse is a handsome octavo, with numerous wood -cuts."— 
American Agriculturist. 



LEA AND BLANCHARD'S PUBLICATIONS. 



YOUATT ON THE PIG. 



THE PIG; 

A TREATISE ON THE BREEDS, MANAGEMENT, FEEDING, 
AND MEDICAL TREATMENT OF SWINE, 

WITH DIRECTIONS FOR SALTING- PORK, AND CURING- BACON AND HAMS. 
BY WILLIAM YOUATT, V. S. 

Author of " The Horse," " The Dog," " Cattle," " Sheep," &c., &c. 

ILLDSTRA.TED WITH ENGRAVINGS DRAWN FROM LIFE BY WILUAM HARVEY. 

In one handsome duodecimo volume, extra cloth, or in neat paper cover, price 50 cents. 
This work, on a subject comparatively neglected, must prove of much use to farmers, especially 
in this country, where the Pig is an animal of more importance than elsewhere. No work has 
hitherto appeared treating fully of the various breeds of swine, their diseases and cure, breeding, 
fattening, <kc., and the preparation of bacon, salt pork, hams. &c., while the name of the author of 
" The Horse," " The Cattle Doctor," &c., is sufficient authority for all he may state. To render it 
more accessible to those whom it particularly interests, the publishers have prepared copies in 
neat illustrated paper covers, suitable for transmission by mail ; and wliich will be sent through 
the post-office on the receipt of fifty cents, free of postage. 

CLATER AND YOUATT'S CATTLE DOCTOR. 



EVERY MAN HIS OWN CATTLE DOCTOR: 

CONTAINING THE CAUSES, SYMPTOMS AND TREATMENT OP ALL 
DISEASES INCIDENT TO OXEN, SHEEP AND SWINE; 

AND A SKETCH OF THE 

ANATOMY AND PHYSIOLOGY OF NEAT CATTLE. 

BY FRANCIS CLATER. 

EDITED, REVISED AND ALMOST RE-WRITTEN, BY 

WILLIAM YOUATT, AUTHOR OF "THE HORSE." 

WITH NUMEROUS ADDITIONS, 
EMBRACING AN ESSAY ON THE USE OF OXEN AND THE IMPROVEMENT IN THE 
BREED OF SHEEP, 
BY J. S. SKINNER. 
WITH NUMEROUS CUTS AND ILLUSTRATIONS. 
In one 12mo. volume, cloth. 
"As its title would import, it is a most valuable work, and should be in the hands of every Ame- 
rican fanner ; and we feel proud in saying:, that the value of the work has been greatly enhanced 
by the contributions of Mr. Skinner. Clater and Youatt are names treasured by the farming com- 
munities of Europe as household-gods ; nor does tha* of Skinner deserve to be less esteemed in 
America,."— Ainerican Farmer. 



CLATER'S FARRIER, 



EVERY MAN HIS OWN FAKRIER: 

: CAUSES, SYMPTOMS, AND MOST APPRO YED IV 
OF THE DISEASES OF HORSES. 



CONTAINING THE CAUSES, SYMPTOMS, AND MOST APPRO YED METHODS OF CURE 
OF THE DISEASES OF HORSES. 



Author of " Every Man his own Cattle Doctor," 

AND HIS SON, JOHN CLATER. 

FIRST AMERICAN FROM THE TWEN1Y-EIGHTH LONDON EDITION. 

WITH NOTES AND ADDITIONS, 

BIT J. s. skz£t:^z:r. 

In one 12mo. volume, cloth. 



LEA AND BLANCHARD'S PUBLICATIONS. 

HAWKER AND P ORTER ON SHOOTING. 

INSTRUCTIONS TO YOUNG SPORTSMEN 

IN ALL THAT RELATES TO GUNS AND SHOOTING. 

BY LIEUT. OOL. P. HA-WKER. 

FROM THE ENLARGED AND IMPROVED NINTH LONDON EDITION, 

TO WHICH IS ADDED THE HUNTESTG AND SHOOTING OF NORTH AMERICA, WITH 

DESCRIPTIONS OF ANIMALS AND BIRDS, CAREFULLY COLLATED 

FROM AUTHENTIC SOURCES. 

BY "W. T. PORTER, ESQ" 

EDITOR OF THE N. Y. SPIRIT OF THE TIMES. 

In one large octavo volume, rich extra cloth, with numerous Illustrations. 

" Here is a bonk, a hanJ-book, or rather a text-book — one that contains the whole routine of the 
science. It is the Primer, the Lexicon, and the Homer. Everything is here, from the minutest 
portion of a gun-lock, to a dead Buffalo. The sportsman who reads this book understandingly, may 
pass an examination. He will know the science, and may give advice to others. Every sportsman, 
and sportsmen are plentiful, should own this work. It should be a " vade mecum." He should 
be examined on its contents, and estimated by his abilities to answer. We have not been without 
treatises on the art, but hitherto they have not descended into all the minutiie of equipments and 
qualifications to proceed to the completion. This work supplies deficiencies, and completes the 
sportsman's library." — U. S. Gazette. 

" No man in the country that we wot of is so well calculated as our friend of the ' Spirit' for the 
task he has undertaken, and the result of his labours has been ttiat he has turned out a work which 
should be in the hands of every man in the land who owns a double-barrelled gun." — N. O. Picayune. 

"A volume splendidly printed and bound, and embellished with numerous beautiful engravings, 
which will doubtless be in great demand. No sportsman, indeed, ought to be without it, while the 
general reader will find in its pages a fund of curious and useful informal-ion." — Richmond Whig. 



BY WILLIAM YOUATT, 

Author of " The Horse," &c. 

WITH NUMEROUS AND BEAUTIFUL ILLUSTRATIONS. 

EDITED BY E. J. LEWIS, M. D. &c. &c. 

In one beautifully printed volume, crown octavo. 

LIST OF PLATES. 

Head of Bloodhound— Ancient Greyhounds— The Thibet Dog— The Dingo, or New Holland Do^— 

The Danish or Dalmatian Dog— The Hare Indian Dog— The Greyhound— The Grecian Greyhound 

— Blenheims and Cockers — The Water Spaniel — The Poodle — The Alpine Spaniel or Bernardine 

Dog— The Newfoundland Dog— The Esquimaux Dog— The English Sheep Dog— The Scotch Sheep 

Dog — The Beagle — The Harrier — The Foxhound — Plan of Goodwood Kennel — The Southern 

Hound— The Setter— The Pointer— The Bull Dog— The Mastiff— The Terrier— Skeleton of ths 

Dog — Teeth of the Dog at seven different ages. 

" Mr. Youatt's work is invaluable to the student of canine history; it is full of entertaining ana 
instructive matter for the general reader. To the sportsman it commends itself by the large amount 
of useful information in reference to his pecuhar pursuits which it embodies — information which 
he cannot find elsewhere in so convenient and accessible a form, and with so reliable an authority 
to entitle it to his consideration. The modest preface which Dr. Lewis has made to the American 
edition of this work scarcely does justice to the additional value he has imparted to it; and the 
pubhshers are entitled to great credit for the handsome maimer in which tliey have got it up." — 
North American. 

THE SFORTSm.a]^'S LIBHARir- 

OR HINTS ON HUNTERS, HUNTING, HOUNDS, SHOOTING, GAME, DOGS, GUNS, 

FISHING, COURSING, &c., &c. 

BY JOHN MILLS, ESQ., 

Author of " The Old English Gentleman," &c. 

In one well printed royal duodecimo volume, extra cloth. 



OR SPECTACLES FOR YOUNG SPORTSMEN. 

BY HARRY HIEOVER. 

In one very neat duodecimo volume, extra cloth. 

"These lively sketches answer to their title very well. V/herever Nimrod is welcome, there 

should be cordial greeting for Harry Hieover. His book is a very clever one, and contains many 

instructive hints, as well as much Ught-hearted reading." — ExamiiKr. 

T^S BOG ilZ7D TiSE SPORTSI^iLSff, 

EMBRACING THE USES, BREEDING, TRAINING, DISEASES, ETC., OF DOGS, AND AN 

ACCOUNT OF THE DIFFERENT IHNDS OF GAME, WITH THEIR HABITS. 

Also, Hints to Sliooters, with, various useful Recipes, &.c», &c» 

BIT J. S. SKINNER. 

With Plates. In one very neat 12mo. volume, "*xtra cloth. 



LEA AND BLANCHARD'S PUBLICATIONS. 

FRANCATELLI'S IVIO DERN FRENCH COOKERY. 

THE MODERN COOK, 

A PRACTICAL GUIDE TO THE CULINARY ART, IN ALL ITS BRANCHES, ADAPTED AS 

WELL FOR THE LARGEST ESTABLISHMENTS AS FOR THE USE 

OF PRIVATE FAMILIES. 

BY CHARLES ELME FRANCATELLI, 

Pupil of the celebrated Careme, and late Maitre D'Hotel and Chief Cook to her Majesty the Queen. 
In one large octavo volume, extra cloth, with numerous illustrations. 

" It appears to be the book of books on cookery, being a most comprehensive treatise on that art 
preservative and consei-vative. The work comprises, in one large and elegant octavo volume. 1447 
recipes for cooking dishes and desserts, with numerous illustrations ; also bills of fare and direc- 
tions for dinners for every month in the year, for companies of sLx persons to twenty-eight. — Nat. 
Intelligencer. 

" The ladies who read our Magazine, will thank us for calling attention to this great work on the 
noble science of cooking, in which everybody, who has any taste, feels a deep and abiding interest. 
Francatelli is the Plato, the Shakspeare, or the Napoleon of liis department ; or perhaps the La 
Place, for his performance bears the same relar.ion to ordinary cook books that the Mecanique 
Celeste does to DaboU's Arithmetic. It is a large octavo, profusely illustrated, and contains every- 
thing on the philosophy of making dinners, suppers, etc., that is worth knowing. — Graham^ s Magazine. 



REDUCED TO A SYSTEM OF EASY PRACTICE. FOR THE USE OF PRIVATE FAMILIES. 

IN A SERIES OF PRACTICAL KECEIPTS, ALL OF WHICH ARE GIVEN 

WITH THE MOST MINUTE EXACTNESS. 

BY ElilZA ACTON. 

WITH NUMEROUS WOOD-CUT ILLUSTRATIONS. 

TO WHICH IS ADDED, A TABLE OF WEIGHTS AND MEASURES. 

THE W^HOLE REVISED AND PREPARED FOR AMERICAN HOUSEKEEPERS. 

BY MRS. SARAH J. HALE. 

From the Second London Edition. In one large 12mo. volume. 

"Miss Eliza Acton may congratulate herself on having composed a work of great utihty, and one 
that is speedily finding its way to every ' dresser' in the kingdom. Her Cookery-book is unques- 
tionably the most valuable compendium of the art that has yet been pubhshed. It strongly hicul- 
cates economical principles, and points out how good things may be concocted without that reck- 
less extravagance which good cooks have been wont to imagine the best evidence they can give of 
skill in their profession."— iondow Morning Post. 

PLAIN AND PRACTICAL DIRECTIONS FOR COOKING AND HOUSEKEEPING, 

•WITH UP-WARDS OF SEVEN HUNDRED RECEIPTS, 

Consisting of Directions for the Choice of Meat and Poultry, Preparations for Cooking ; Making of 

Broths and Soups ; Boihng, Roasting, Baking and Frying of Meats, Fish, &c. ; Seasonings, 

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PREFACE. 

This illustrated Manual of" Sports, Pastimes, and Recreations," has been prepared with especial 
regard to the Health, Exercise, and Rational Enjoyment of the young readers to whom it is ad- 
dressed. 

Every variety of commendable Recreation will be found in the following pages. First, you have 
the little Toys of the Nursery ; the Tops and Mai-bles of the Play-ground ; and the Balls of the 
Play-room, or the smooth Lawn. 

Then, you have a number of Pastimes that serve to gladden the fireside ; to light up many faces 
right joyfully, and make the parlour re-echo with mirth. 

Next, come the Exercising Sports of the Field, the Green, and the Play-ground ; followed by 
the noble and truly English game of Cricket. 

Gymnastics are next admitted ; then, the deUghtful recreation of Swimming ; and the healthful 
sport of Skating. 

Archery, once the pride of England, is then detailed ; and very properly followed by Instructions 
in the graceful accomplishment of Fencing, and the manly and enlivening exercise of Riding. 

Anghng, the pastime of childhood, boyhood, manhood, and old age, is next described ; and by 
attention to the instructions here laid down, the lad with a stick and a string may soon become an 
expert Angler. 

Keeping Animals is a favourite pursuit of boyhood. Accordingly, we have described how to rear 
the Rabbit, tlie Squirrel, the Dormouse, the Guinea Pig, the Pigeon, and the Silkworm. A long 
chapter is adapted to the rearing of Song Birds ; the several varieties of which, and their respective 
cages, are next described. And here we may hint, that kindness to Animals invariably denotes an 
excellent disposition ; for, to pet a little creature one hour, and to treat it harshly the next, marks 
a capricious if not a cruel temper. Humanity is a jewel, wiiich every boy should be proud to wear 
in his breast. 

We now approach the more sedate amusements — as Draughts and Chess ; two of the noblest 
exercises of the ingenuity of the human mind. Dominoes and Bagatelle follow. With a know- 
ledge of these four games, who would pass a dull hour in the dreariest day of winter ; or who 
would sit idly by the fire ? 

Amusements in Arithmetic, harmless Legerdemain, or sleight-of-hand, and Tricks -with Cards, 
will delight many a famQy circle, when the business of the day is over, and the book is laid aside. 

Although the present volume is a book of amusements. Science has not been excluded from its 
pages. And why should itbel when Science is as entertaining as a fairy tale. The changes we 
read of in little nursery-books are not more amusing than the changes in Chemistry, Optics, Elec- 
tricity, Magnetism, &c. By understanding these, you may almost become a little Magician. 

Toy Balloons and Paper Fii-eworks, (or Fireworks without Fire,) come next. Tlien follow In- 
structions for Modellnig in Card-Board; so that you may huild for yourself a palace or a carriage, 
and, in short, make for yourself a little paper world. 



Puzzles and Paradoxes, Enigmas and Kiddles, and Talking with the Fingers, next make up plenty 
of exercise for " Guess," and " Guess again." And as you have the "Keys" in your own hand, yoa 
may keep your friends in suspense, and make yourself"^ as mysterious as the Sphynx. 



A chapter of Miscellanies — useful and amusing secrets — winds up the volume. 

The •' Treasury" contains upwards of four hundred Engravings ; so that it is not only a collection 
of "secrets worth knowing," but it is a book of pictures, as full of prints as a Christmas pudding 
is of plums. 

It maybe as well to mention that the " Treasury" holds many new games that have never 
before been printed in a book of this kind. The old games have been described afresh. Thus it 
is, altogether, a new book. 

And now we take leave, wishing you many hours, and days, and weeks of enjoyment over these 
pages ; and we hope that vou nmy be as happy as this book is brimful of amusemewt. 



,« 



J 615 



